I've always been of the belief that Adrian didn't join in with the rest of the band in that lip-synch video because it was his song, he wanted it promoted, and he felt serious about it. Other than that, yeah, he is a serious performer, and he's more concerned than all other members about messing something up. Shirley's studio diaries have some insight on that. I guess he was the driving force behind dropping Paschendale and Brighter Than a Thousand Suns from the 2010 setlist. They were both his songs, and they reportedly kept screwing them up.
Bruce and Steve on the other hand, aren't best mates as is well-known, and don't seem to have the sort of relationship that allows them to play around with each other in that way.