No look at his calves before and after.. He has not put on muscle. Just stripped off his fat to reveal abs.
But even many competitive bodybuilders have legs that often look like they've never been trained.
The guy looks good, but just looking at the rest of his physique aside from his legs, it's clear he put on muscle. He had manboobs before and his chest is now muscular and well defined, along with his shoulders. It wasn't just peeling back fat. To put on that much muscle while losing weight in such an extreme calorie deficit seems unusual.
Honestly, I'm not entirely convinced it's the same guy, but if it is, it's not that crazy to speculate he's using some sort of gear.