I once heard John Landis say that he had to record the singing from Aretha Franklin and James Brown live on the set of The Blues Brothers because they never sang a song the same way twice. After watching this performance, which I missed when it was originally on, I think George Michael was the same way.
I read that no live version of the solo at the end of “Comfortably Numb” (and certainly others of theirs) is identical.