His legs are really, really wide. Does that matter? Does it offer more power when going up? Nobody I know squats like that.
Part is personal preference and part is equipped vs. raw lifting.
Squatting wide lets you sit back more, which does 2 things.
1- it keeps your knees back, reducing stress on them. There are top guys who lift equipped with no knee wraps because they can sit far enough back to not put enough stress on their knees to need them.
2- It's a shorter range of motion that favors bigger muscle groups. The problem is that raw lifters would tear a groin trying to go ultra wide.... this is one way that equipment adds to the lift. In tight briefs or a suit I can squat super wide without my hips taking a beating.
Now, some equipped guys Do squat narrower ( guys like Yarmbash) and some go even wider ( Vogelpohl).... it's personal preference.