I keep seeing reports that Nex walked into the living room the next day, complaining of a headache, collapsed, and was rushed to the hospital where they died.

Everything about that, and their initial state, immediately after the fight, are classic head trauma symptoms. If what ultimately killed Nex was something like a subdural hematoma, then I guess you could argue that the death was not directly a result of the trauma? But the causal chain of events is incredibly obvious.