He’s still doing aerobic work. Look at a wrestler like Romero and the techniques he uses.
Physiologically Humans have fast and slow twitch muscle fibres. People have a majority of one or the other. That’s why we have sprinters and long distance athletes.
Romero explodes-rests-explodes whereas Usman goes at 70% the whole time. Look at the body types Usman is ripped but almost like a swimmer.
To get really simplistic while they could probably do both they’d run the risk of injury/cramp etc. Usman would probably fatigue a lot worse if he exploded like Romero does.
Interesting fight to look at is Rashad Evans vs Phil Davis.
Evans the explosive fighter wore Davis the endurance fighter out by using explosive techniques and transitions due to Davis countering with Explosive techniques.