[Continued since I was in a hurry earlier...]
It could be assumed then that since being flatfooted doesn't allow one to make AoOs, then being denied one's dex bonus has the same effect.
Thus getting rid of the unusual circumstance that you can make AoOs against invisible provoking opponents.
At least, that's the reasonable explanation for it.
If you want to be blindly literalist about it... then you would say that being flatfooted is different from being "denied one one's dex bonus" and thus irrelevant (as what Hyp is saying).
Geez, do I have to spell everything out for you, Hyp? Lol