Oh shit, so you've judged him on his Youtube highlights? Sorry, I was under the impression that you'd regularly been watching him play.
I've seen Busquets play dozens of times, and his passing choices under pressure is light years ahead of what I've seen of Carvalho.
Busquets, Yaya and Xabi Alonso play lots of square and backwards passes too, I'm sure the stats will back that up. But it's only when watching them in full games and seeing their speed of thought and quality of pass under pressure in a real game situation that you can fully appreciate how much better their pass selection is than say Fernando, Javi Garcia or De Jong.
The Youtube highlights reels can look impressive for any player. The stats can be very deceiving and certainly don't give you an accurate analysis on their own.
I'd be happy to take the opinion of someone who'd watched dozens of games of Carvalho and made an informed analysis. But if your basing it on Whoscored stats and Youtube highlights, you're really not in a position to argue against my point because I've seen those too.