Although some people are claiming it is a solid wheel, not a cover. My guess is a cover on those though.
There's been posts where the poster talked to an owner/employee and they confirmed it's a cover. I think it's pretty well established it's a cover. It's probably about 90% certain that picture is what it looks like underneath.
I'm not sure why Tesla does not post official size information concerning the wheels. ( offset / bolt pattern ). It could only help them...right?
How would it help them? So people have a way to go aftermarket or otherwise not purchase the 19" upgrade?