The version heard on 20/20 (and as session tapes on a recent SOT CD) is little more than a rehearsal. There is in existence a longer, nearly finished recording of the song. The only reason I can think of that it wasn't used on the FRIENDS/20/20 two-fer is that it simply hadn't turned up at that time.
I actually think it's Carl singing the "foolish pride" line, not Dennis.