The face pic you've chosen isn't right, but the ring is chopped off, I think in the one you're questioning. Only part of the gem is on it, I believe. Additionally, I don't think the "contours" of Birdo's legs are included in the suit, while they normally would be. Birdo's legs aren't clay-like, they're shaped differently in the art you supplied.
I'd say it's a fake because his head doesn't sit right on his shoulders in that picture. In marketing, pictures get mirrored all the time.
However, it's more likely that it's just poor artwork by Sega. Who'd go through the effort to shop that? Likely, a Sega artist almost traced Birdo's arms and head from official art supplied by Nintendo, and attempted Birdo's body in a skater's suit after that. It didn't come out great, compared to the art you posted, but it could've been worse. Likely, someone flipped it, and yadda dadda da.