It isn't a glitch. Since he represents having all 99's, it was kind of obvious that someone like him would be a little....'skill-y'. I never thought they would make him so damn life like though.
He runs around training different things around Varrock: Herblore/alching in the bank, Smithing at Horvik's, and a lot more. Another player and myself even tried trapping him and he teled.
That guy is seriously something...