Sorry if this question has been asked, but it was difficult to search through given the volume of Twin Paradox questions.
My question isn't with the twin paradox per se; it's with what the traveling twin observes when they're changing their direction of travel.
So, the twin heads away from Earth at, say, $0.8c$ for $t$ seconds. All this time, things on Earth are moving slowly--less time appears to have elapsed on Earth than has on their spaceship. However, after $t$ seconds the time comes to change direction and head back to Earth at $0.8c$ for another $t$ seconds. When this happens, their plane of simultaneity changes:
However, let's say that the traveling twin isn't able to somehow accelerate instantaneously, so their plane of simultaneity doesn't abruptly change its angle but rather sweeps through the Minkowski diagram. As it's sweeping it stands to reason that the traveling twin would see Earth on something akin to fast-forward, until they finished accelerating and once again observe ("future") Earth as moving slower than they are (at least I think--I'm a layman, so it's completely possible that I'm totally wrong at any point).
While they are under accleration, and Earth appears to be on fast-forward (IF it appears to be on fast-forward), why don't they observe faster than light photons racing across the Atlantic in undersea cables? Does the size of Earth get perfectly squished down due to length contraction? That only happens in the direction of travel, correct?