Detectable gravitational waves can have a frequency from 10^-7 Hx to 10^11 Hz. Frequency is largely irrelevant to whether they are considered waves.
I find it best in discussions to first be sure we all use the same term to describe the same thing. So I will at first avoid the term "wave", in order to best define it.
What matters is that they are propagating vibrations.
So let us consider, for simplicity, our earth-moon system, in the simple 2-dimensional "rubber sheet" model, with all other nearby bodies ignored. The planets are heavyish frictionless disks.
We consider them, initially, at rest, not rotating about each other. Each makes a dent or dimple in the sheet which reaches the other. In fact, since both are within eachother's dimple, we end up with the sum of the two being a sort of hourglass-shaped dimple.
Now we mark several points, equally spaced, on the perimeter of the "earth" disk. We place a "rubber stretch detector" at each marked point, and naturally, it detects a little more stretch in the direction of the "moon" disk, with more stretch the deeper that detector is within the dimple from the moon disk.
We start moving the two disks slowly about each other. The stretch-detectors at the points we marked will detect a "waveform" - which, for clarity I will call a "tide" - of increasing and then decreasing gravitational power.
The speed of the ups and downs in our marked points' measurement of this tide depend entirely on the speed we make the disks orbit around each other.
More importantly, the speed that the tide travels between the different detectors, also depends entirely on the speed with which we move the disks.
This is because the dimple from the "moon" plate stays the same, it's just that as the two plates orbit each other, the measuring point moves deeper into or farther out of the dimple caused by the moon plate. Because the orbits are circularish, the changes in measurements at each point happens to look like a waveform.
Next we drop a marble many feet away on the sheet. Ripples will spread out from it. They are traveling at the propagation-speed of the sheet ("light speed", if you will), and are not static to a dimple of the marble. They will eventually pass the detectors on our earth plate and be measured as a wave-shaped ripple. Another thing to note about these ripples is that they rise up out of the sheet as well as sinking into it: they are bidirectional.
Place a vibrator on the sheet some distance away. Again, our detectors measure ripples, not static dimples, moving at the propagation speed of the sheet.
It is hopefully intuitively obvious to us all that ripples are small, propagating bidirectional deformations, while tides are large, relatively static, unidirectional deformations.
The term "gravitational wave" refers only to the propagating ripples, not the static tide.
We can now address the specific claims made in the OP.
This is the SAME gravitational wave effect measured by the LIGO
This is not a gravitational wave, this is a measurement of tides caused by the movement of a single detector within the earth-moon dimple. If there had been a second detector, it would have been clear that these tides do not propagate across the earth at the speed of light, but at the speed of the movement of the moon.
Without a specific link to the claims you are debating, my response (and everyone else's) can only be guesswork. It's entirely possible that the operators of LIGO have gone bonkers and are reporting tidal effects as gravitational waves or something, but since we don't have access to this, we instead have to assume they did not.
LIGO actually detects, then filters out, this local gravitational wave
This uses the term "gravitational wave" incorrectly. It is more correct to say, "LIGO actually detects, then filters out, this local gravitational tidal noise."
in order to detect the remote ones producing the ultra weak
gravitational waves from binary black holes. Although the sensitivity
required to detect them is 3 orders of magnitude higher in both
frequency and amplitude,
All the above appears correct.
the LIGO "gravitational" waves are otherwise
exactly the same "gravitational" waves already discovered in 1981 in
our own solar system.
The above is correct only in given the flawed definition of "gravitational wave" corrected already above.
It is more correct to say "The LIGO-filtered-out gravitational tidal noise is indeed the same gravitational tidal signal that was measured in 1981, and discovered in 1687 when Newton discovered that the moon was the cause of tides."
The proof is in the fact that LIGO detects gravitational waves but can
NOT detect "tidal" gravity waves.
This is technically true: it can't detect them because it filters them out, as stated in the very first sentence I quoted above.
Thus categorization of Zumberge's waves as "tidal" gravity is incorrect
Nope, that's exactly what was being measured.
as tidal waves are those between two surfaces as a consequence of gravity.
More correctly, "tidal gravitation effects are those measured at a point as a mass moves about that point."
These cannot be detected by an interferometer.
Interferometers are explicitly designed to detect stretching of the "rubber sheet". The moon's gravity well stretches the rubber sheet. The movement of the moon about the earth moves its gravity well relative to the earth, causing tidal effects where the rubber sheet gets stretched more or less.
So the above is blatantly false. It would be more accurately written: "These must be very accurately filtered out of the interferometer measurements in order for the far smaller effects of gravitational waves to be detectable."
Zumberge's measurements are of gravitational
variations itself, hence gravitational.
Yes. Changes in the strength of gravity as felt on the surface of the earth, due to the tidal forces of the moon moving around it.
Why has the 1981 work of Zumberge, Rinker and Faller been ignored?
Because in the paper you linked, they were just saying "Hey, we've developed this much smaller apparatus for measuring these tidal effects we've known about for thousands of years. It's portable, check it out." They are not claiming to have discovered any new gravitational effect; they are just showing the design of a better piece of equipment for measuring previously known effects.
Their graph was displayed without fanfare because everyone already knows about tides. The interest of their apparatus is that it lets one (after canceling out tidal effects) measure subtle variations in gravity due to geological effects.
So, corrected for errors in definition of "gravitational wave", and understanding of how interferometers work, the OP contains no unusual claims, but the question itself then disappears.
Some people invented a cool portable gizmo for measuring the strength of gravity at any point on earth. As many had before them, they then measured this over time, and drew a graph of the tidal effects over a period of a few days. That's all.