The point is that you could swap what OS it is in the background and it wouldn’t make a difference that it’s Linux. The Steam Deck could be running Windows with Big Picture on top of it and no one would be the wiser. It’s misleading to say that Steam Deck users are Linux users if they don’t even use any of the Linux environment.
I’d probably call Big Picture the Desktop environment in this case. Yes it’s a simplified linux experience, but it’s not not linux.
The point is that you could swap what OS it is in the background and it wouldn’t make a difference that it’s Linux. The Steam Deck could be running Windows with Big Picture on top of it and no one would be the wiser. It’s misleading to say that Steam Deck users are Linux users if they don’t even use any of the Linux environment.
But that’s true for anything. you could swap out the OS under gnome and most users wouldn’t notice either.