I think the ref pulled the trigger a little soon there. None of the those punches in that final flurry were really hurting Manfredo - it was simply the speed they were coming at him meant he couldn't stand up straight to throw a few back. But he was in no danger of going down and wasn't taking damage.
Even Joe admitted it was a bit early, but Manfredo had forgotten you usually need to throw punches in a fight to win.
No wonder his nose looks like that.