Those 2 boss fights are the ones where DPS on the boss is light. It is probably the only fights he could hold aggro on, unless everyone held back. People did stuff like that as a gimmick sometimes, it doesn't mean <REDACTED>. It was horribly suboptimal, but doing it once of twice might be fun. You can probably find old videos of Shadow priests, and moonkin tankig Onyxia too. But, like I said they did as a gimmick. It in no way implies they were decent tanks in vanilla.