Legal? Always?

[IK13]

Trivial situation - attacker and blocker. One lands on the foot of the other. No foot is completely beyond the center line. Happens very often and besides being the #1 source of injuries, it is (generally) legal.

But is it always?

What if the person on top, pinning the other, does not move fast enough making the pinned player unable to move to play the ball? “Fast enough” here is very relative, a fraction of a second could be too long when the ball is falling.

The situation seems to fit precisely the definition for interference:

15.2.3 Interference
It is a fault to interfere with an opponent. Interference is defined as contact that hinders an opponent’s opportunity to play the ball. Inadvertent contact that does not affect an opponent’s ability to make a play shall not be considered interference.

And is not cleared by:

15.2.4.2 Contacting the opponent’s court with the feet is permitted, provided
some part of the penetrating foot or feet remains in contact with or directly
above the center line, and there is no interference with opponents.