Can confirm the exact same thing happened to me, same with losing my Legion class hall title. This seems really bad tbh and is also likely able to be exploited with knowledge point treasures now that I think about it. The strange thing I noticed though is all the quests I completed seem to be marked as warbound complete, which means the game still knows these quests were completed at some point. The amount of progress lost is so comprehensive I’m really doubting Blizzard will be able to fix it all.