Di-poles work best when people are positioned close to them. When people are close to a direct firing speaker they get what I call that speaker in the ear effect. That one speaker very close to them will call attention to itself. Di-poles work good for that scenario as drivers are not aimed at the listener. There is no problem using di-poles for back speakers but you have to make sure the phase is correct. To do that you reverse sides of the back speakers, left speaker goes on the back right and right speaker on the back left. This is if you are using di-poles for the side surrounds as well. The backs don't need to be reversed if the side surrounds are direct firing or bi-poles.
You're referring to dipoles as having a designated left and right speaker. When I bought my SA-ADP in wall speakers they weren't designated as a left and a right speaker. I'm assuming the ADP-590's are the same way, no designation of left or right speakers. Does Paradigm have any speakers that designate if they're left or right speakers? And you mention that with dipoles there's no speakers that would be aimed directly at the listener. With the Paradigm ADP speakers...doesn't the woofer face directly out towards the listener? If what you're describing is a dipole speaker (i.e. speakers that are designated left and right, speakers not facing the listener), it doesn't sound like the Paradigm ADP speakers are true dipoles (maybe that's why they call them Adapted DiPoles).