And going through it would not be compliant.Yes, I agree, too. Provided the (intact) cables go through the box, then nothing short of crass stupidity is going to result in loss of the blank plate which 'announces' their possible presence. As you say, just 'borrowing the safe zone' created by some other accessory, without one's cable going through the back box of that other accessory, would not be totally foolproof.
Read the 2nd sentence of 522.6.202(i) very carefully.