Siver was getting pounded, but I really hate stoppages like that. It seems like the tactic at the point is to throw as many punches as you can, and wait for the ref to stop it because the guy isn't "defending himself". You know what you do when someone is throwing a barrage of punches at you? You cover up and wait for it to end.
In this instance it wasn't such a big deal. Siver had nothing to offer... but there have been several fights where refs seem to think 20 punches hitting someone's arms = not defending. I hate that shit.