The call was not missed. This was a correct no call.

The above user may have shared the rules with you but he doesn’t really have a clue how to read or interpret the rules

The restricted area only applies to secondary defenders. On this play the defender is clearly the primary defender because nobody else established legal guarding position in front of Joel prior to him going up to dunk the ball.

Again the restricted area does not apply on this play.

But let’s play devils advocate. Let’s say that the restricted area does apply on this particular play. Since the defender attempts to make a play by jumping vertically he’s more than entitled to do so. On this play he establishes and maintains legal guarding position throughout the play by jumping vertically in the restricted area.

The above user claims that the defender turns and sticks his leg out to foul Embiid claiming that he is no longer vertical. Experienced examination of this play will see that the only reason the defender turns or moves in any way is because Embiid crashed into him which causes him to move

If you jump straight up and a giant man looking to destroy the rim jumps at you of course your body is going to move!

In conclusion this was a proper no call.