I know that an airplane can make a roll that keeps the fluid in the cup, but when usual commercial planes fly, they don't do stunts, so usually there's no centrifugal force to mimic gravity. When a big jet points its nose down or up people and fluids feel it pretty much as if they were on the ground on a slanted flat surface as one of its edge is being raised or lowered.

Sure, this would probably worth next to nothing in turbulence, but in a simple take off and landing (where MCAS is already active and depends on AoA) it might help.

And of course I might be completely ignorant of most of the relevant problems with using any kind of gyroscopic or acceleration based sensor.