It's due to categories that don't use the IGT as basis like the runs where you unlock all endings for instance.

There is an important reason I've banned PSP emulators. The fact is they aren't on the same level of consistency as PSX emulators are. Nowadays there are PSX emulators available that can perfectly emulate a real PSX console to the point where there are next-to-no in-game differences or bugs when comparing the two. PSP emulators are improving a lot, but they are still buggy and aren't really reliable enough to use for a run. This is a lot more important in a game like Tekken where a consistent 60 FPS is needed.

The deal with the PS3 version of DR is that it doesn't have any real categories you could run. There's Time Attack, but that already has online leaderboards so I don't see any reason to include that here. Otherwise, pretty much everything is already unlocked and ranks are obtained through online play. The PSP version has endings the user can unlock; on the PS3 version, those are already unlocked.