Well sure Move support in Flower would be more impactful as motion controls is what the whole controls are based upon, but while I do agree they wouldn't add much to the experience in Journey, I do believe Move is better suited for this sort of camera controls, to the point that no Move owner would ask for a right stick alternative. Which on the other hand is the case with DS3 users.
Add to that the ease of implementation (can't stress this enough - I wouldn't discuss this matters if Move implementation would have required serious effort) and I just don't see why it's not there already in the first place.
It seems to me TGC wants people to enjoy motion camera controls so why not offer the best solution for that? Heck, you might even sell a few extra copies to some of those 9m Move owners out there looking for compelling content. Of course they all own a DS3 as well, but that's no guarantee they'd buy your game. Move support is no guarantee either, but it's an extra "lure" worth taking advantage of IMO. Cover all the bases etc.
Good thanks! Trying to get Journey to support Move so I can talk about it on iWaggle3D