I have the same issue, if I delete a tab group on safari 15.2 (17612.3.6.1.6) on macOS 12.1 , It immediately sync back. It also shows up 2 times.. so I have for example 2 folders with the same content. Tried removing them both first the first secondly the second, all syncs back. No clue which is the master. Should try to do it on my iPad or iPhone and see what the outcome is on that.