Do you know where one could read more about Apple's technique? I don't know much about lenticular displays or why the trick only works in one direction (presumably the horizontal one).
The Wikipedia article might explain it better: https://en.wikipedia.org/wiki/Lenticular_lens
It could work in both dimensions but you're sacrificing even more resolution by doing it that way. For example imagine you have a 1000x1000 pixel display (I just made this resolution up) and you stick a 1D lenticular screen on top with a pitch of 10 pixels. You've effectively split the display into 10 separate 100x1000 displays that are each view from a different angle. You could instead use a 2D lenticular screen and split it up into 100 100x100 displays viewable from a different angle in a 10x10 grid at virtually no extra $ cost. However, you're displaying at 1/10th the resolution just to be able to support perspective-correct views from above or below, which are way less common than from the side.
I'm guessing (?) Apple's approach is similar.