The only thing I can think of in favour of McCartin in that incident is that he's flushed himself, that it wasn't the sort of hit that means anything to him long term / that it's more just a strange looking incident.
It's not necessarily the biggest punches that result in the clean KO. My understanding is that it's got something to do with the angle the head and neck twist at, once punched, which closes blood flow resulting in that dramatic collapse. I'm not talking about every KO but those ones that don't seem to hit as hard as the other punches that land and take an otherwise fit fighter straight down.
Could this have happened to McCartin? His head was twisted almost right around, almost like he was sleeping on his stomach, at the point of impact? It wasn't really a skull rattler.
But then I hear that clip of him with Garry Lyon and all I could really think was that he's done a bit of gymnastics with his medical advice. Not that I believe the basic claim but, in any event, increased susceptibility to concussion, as a medical diagnosis, isn't really the issue where the main concern is the cumulative impact of big head knocks. Not to mention that Paddy is already clearly more susceptible to concussion.
That's called rattling the cage. The one you don't see coming.