@Watch-man:
Kaido is not Dragon Zoan..
More likely he is Dragon that ate Devil Fruit like Oni or Ogre model(or something else that gave him more intelect/ability to speak and so on). He is creature and not said to be human.
Him being Dragon Zoan would be a lot less interesting than other way around(like with Choppers DF).
Also I guess he didnt wanted to block at all to see what Luffy can do. Beside that perhaps him shrinking to his human form makes him insanely dense so to say. So that he is impossible to kill because of how dense his body becomes thanks to shrinking into smaller form.
That would make X scar on his stomach easy to exmplain - for example Ashura together with second Samurai slashed his Dragon form belly and damaged him. He seems to be more vunerable in Dragon form.
I think both [human Kaido with a dragon zoan] and [dragon Kaido with an Oni zoan] is very much possible, and both scenarios are interesting in their own way.
Dragon Zoan has obviously the parallel with Momonosuke going for it, as well as a possible link to Vegapunk, who tried to artificially create the power.
On the other hand, Kaido being a Chopper-like creature has it's own charme and the potential for some really cool Chopper-Kaido moments. Just imagine both Big Mom and Kaido fighting over Chopper. He would be a super rare species to one and a kindred spirit to the other. The disgusting monster from Paradise is suddenly the hottest shit in the New World!
But maybe he isn't even a natural Dragon, but one of Vegapunks many Dragon experiments. We have seen massive dragons already, Kaido could have been the strongest specimen. The specimen that escaped and got caught numerous times, and then ultimately stumbled upon a mythical hito fruit (the counterpart to Sengoku's Buddha Zoan). Again, this would create a convenient link to Vegapunk (who's bound to show up really soon anyway).
As it stands the chapter makes it look like he has a dragon zoan, because he turned back into a human after being pummeled (shrinking, getting "weaker", which turned off the ability). But it's also possible that the opposite was the case. He turned into his true dragon form because of careless drunkenness, while the punches sobered him up to the point that he found his composure.
Whatever it is, I think it's fun that people consider both ways. There is no need to religiously defend anything, just let the theories flow and see what happens.