I think the only thing that almost cost him was naivety. He thought he had it done, chased the ko and got tagged. Did well to hang on and then his youth helped him recover.
The stoppage was spot on imo, he'd been floored twice in 30 seconds as wasn't offering a defence. He wasn't gonna make the last. And if he did, the 10-12 rounds would imo have been enough to swing it just in Aj's favour for a points win.