Exactly. Everyone is freaking the hell out over complete parity when the only information we have is on resolution and target framerate. There are a hell of a lot more effects that go into making a game look good than just resolution. Even with Watchdogs there were graphical differences apart from resolution. We have no idea what graphical settings were lowered, or how performance was effected by getting unity to 900p on the XB1. Everyone is looking at this issue backwards. It shouldn't be about what the PS4 version isn't getting by being at 900p, it should be about what the XB1 version is losing by being at 900p.
How does reaching resolution parity bring it up to PS4's level? This is my entire point, we have no idea what is going on beyond resolution. There is no way in hell they got the XB1 version to 900p without making sacrifices to performance, graphical settings, or both. The recent preview from Videogamer where they got hands on with the XB1 900p build talks about how poorly the game was running with dips into the low twenties. That alone is a clear sign that sacrifices were made to reach that resolution, and further sacrifices may need to be made in order to smooth out the framerate. Even if all other things are equal, is it still parity if the two version are at 900p, but one of them performs significantly worse than the other?