Silithus is wounded in 8.0.1, the current version and the old version share a common id=81.
Old quests like 9416 cannot be done in the same copy that has 50973.

The only difference i can see so far is the spell time travel Zidormi puts on you to bring you back to the old times (spellid=255152).

Not sure if we have any other way to tell the two phases apart.