I'm not Gurley but I don't get the sense he's being particularly serious. Haven't heard a lot of his interviews but he seems like a decent guy, unlike the bitter, legitimately hateful players we've seen prior (Faulk, Suggs, Bart, LT).
The spelling of the phrase gives me more of a light-hearted vibe than any serious animosity.
As for the Super Bowl performance, I think it's safe to say he was injured, but I suspect we won't know the full-story until some years from now. Any admission from the team that Gurley was in fact injured would probably result in discipline from the league, since he wasn't on the injury report at any stage of the postseason. Hard to gauge his weak performance without that context. That said, I do wholeheartedly agree his play was uninspiring, to say the least.