I think he should have easily seen that KZ was KO'ed, so what argument I'm going to make is a dumb one, admittedly.
But I'm fairly certain that if the ref didn't stop the fight before the bell sounded, technically, a hurt guy can still answer the scorecards. The ref, of course, has full discretion and can call the fight any time up until the official announcement. (See fights where fighters can get DQ'ed after clearly winning the fight, either by the other fighter being unconscious or even after the last bell). But as long as the fighter can get up by himself and answer the call, then KZ would have seen the scorecards and the win, but he had to stand up on his own accord and couldn't be helped by the ref or his corner.
Having said that, any ref wouldn't need to take more than a second to realize KZ was dead as dead and the fight wasn't going to the scorecards.
Additionally, maybe there was some danger to trying to move him alone because of the hunched facedown position KZ fell into? Idk, I'm not a doctor. But yeah, that ref took his real sweet fucking time addressing it. Was it not the same guy who called the terrible Skelly stoppage?