Irahl isn't thinking about the fact that he's still injured, but some unconscious part of him is still keeping track of these extra vulnerabilities and the fact that Vincent's antics are a genuine threat to them. So, there's a fun extra jolt of adrenaline when the roughhousing becomes a little more intentional.

Even when sober, it's easy for Irahl to stop thinking about the point behind violence and just lean into it once it's started. So, when drunk and rowdy, he's very quickly fighting a grin and ramping up how pointedly he's blocking and returning the aggression sent his way.

Of course he's making sure to be a pain in the ass to fight. He's just as clumsy as Vincent is right now, but he isn't battling gravity at the same time. So, anything that he manages to block also gets shoved to the side, and he takes at least a couple of opportunistic pot-shots at whatever limb Vincent happens to be using to prop himself up with at the time, just to give his opponent a harder time than necessary. Just to piss him off.