To go with the qualification somebody mentioned earlier in the thread, I doubt Giannis is guarding the opposing 2 guard most of the time.
That Bucks team is a weird mess, though, especially with Middleton out.
I think it's safe to say Giannis wouldn't play SG on the vast majority of teams in the league.
If you want to list him as a 6'11'' shooting guard, though, it's clear he'd be ahead of AB.