I doubt I can hide from the effects of gravity when I'm close to Earth. We usually don't question this biker is fully experimenting gravity:
It seems to me that the gravity in the A300 is not reduced at all, it's still the same than when flying straight and level. Exactly like the gravity hasn't changed for the stunt biker.
I also often read that the weight appears null, due to the free fall. But again I don't understand... According to Merriam-Webster:
Weight: The force with which a body is attracted toward the earth or a celestial body by gravitation and which is equal to the product of the mass and the local gravitational acceleration.
And that's what I learned: $w = mg$, and because mass and gravity acceleration haven't changed, then it seems weight hasn't changed either.
If gravity and weight haven't changed, then what is reduced actually in so-called reduced gravity? What does really happen to the aircraft and its occupants?
The only thing that I can see as new in free fall is that the different parts of a body (or the of the aircraft) are not anymore ordered from top to bottom by their weight. For example air will not be on top of fuel in the aircraft tanks, and blood will not be moved towards our feet without an action.