He was out of combat from the first punch indeed. However, he wasn't knocked out unconscious in any moment during that barrage. After the first blow he clearly turns during the fall looking for the coming opponent and right after the stoppage, he is immediately interacting with the referee. You don't recover from that first punch by receiving ten more, so that's the reason he wasn't out cold in any moment. At least as out as Terry Etim against Barboza.
That being said, no need to wait for positive indication of uncounsciousness to stop the fight. The fight shoud have been stopped after the first, maximum third blow as he, although partially awake, could do zero to defend himself.