They signed ZERO free agents and have 10 players in their 1st or 2nd year. They had a lot of draft picks and used them all. They were tanking from the start. Holmgren's injury just gives them an excuse, but that was not a team that was making moves like it was trying to win.
Maybe this is part of the issue, but I think I've long disagreed with your definition of tanking. To me, it seems like you label any bad season as tanking. Or any team not making short term moves to improve their current season win total as tanking. To me, that's not tanking. OKC not signing free agents isn't a sign of tanking. OKC trading veterans for youth/picks isn't necessarily tanking. OKC sitting Al Horford, now that's tanking.
The way I see it, tanking is purposely being bad for the sole purpose of improving your draft position.
Rebuilding is focusing on being good 2-5 years in the future, while not worrying about your current win total.
They're similar, and often overlap, but different.
Celtics in '97 tanking. Celtics in '07 tanking, Celtics in '14 rebuilding.
OKC in '21 rebuilding that turned to tanking.
HOU in '21 rebuilding.
ORL without taking a deeper look at their moves, would probably classify them as rebuilding the majority of the time since Dwight Howard left, rather than tanking.