Your spinning his traits negatively to fuel your nascent agenda but RG3 was merely being persistent in the face of adversity and showing supreme confidence in his abilities.

Shanny, as the coach, should be able to see through that though and temper the potentially self-destructive motivations of his players. He's surely had other players tell him they're the best option at their position and they're ready to play, even when they're not.

I'm sure he's pulled lesser players but he knows the Skins ceiling is much higher with RG3 than with cousins so I think he believed what he wanted to believe in this case.