I think a lot of that is just because his body is in transition right now. He knows that the days of barreling towards the rim at 100 mph are coming to a close, so he's doing it less and less often (saving it for crucial moments like in the hawks game today)...I think he's still getting acclimated to his new baseline of basketball shape. TBH I think he's shooting all those iso jumpers because he's realizing he will need to rely way more on that shot as he ages, so he's always practicing it in in-game conditions (but if you notice he tries to do it more only when the game is either close or the cavs are comfortably ahead...he won't dare try that iso joe deep 2 point shot fukkery if they're losing by a decent amount)
Yeah he is conserving his energy. All the greats do this as they get older (Kobe, MJ). He has to shoot more jumpers because driving takes energy out of you.