I think it is completely stupid to allow unsynced runs of any kind. Especially when they have such a good sync system in the game.
Buuut every MMO seems to do this. Basically just don't bother being super hardcore, getting awesome rare things and so on because some time after people will faceroll them and get the things you worked on for months in one evening.
That's how I started to look at it after what happened to coiltower. Like the final witness was a pretty rare title way back, but now nobody who actually cleared it back in the day uses it because they don't want to get mixed up with the people who did it unsynced.
It's stupid that it happens, but what can you do. Gotta allow everyone to have all the rare stuff without putting in the work.