@Baroona - All I see is that you're talking about exceptions more than rules. You're using some of the best fighters to prove your point.
Mike Tyson was the exception moreso than the rule. Boxer's use "fast-twitch" muscles to increase their speed so they get bulkier, however, their stamina lacks. Mike Tyson was known for his speed but that's because in his weight division the people he fought against were much bigger than he was, so he needed to bulk up with fast twitch exercises. Muhammad Ali was more slender than your average Heavyweight as well.
Look at them side by side: https://static.independent.co.uk/s3fs-public/thumbnails/image/2016/06/04/08/muhammad-ali.jpg?w968h681 [Ali]
https://talksport.com/wp-content/uploads/sites/5/2020/04/NINTCHDBPICT000575474879.jpg?strip=all&w=960&quality=100 [ Mike Tyson]
The difference is night and day due to their sizes. Mike was built with the necessary advantage of his small frame which was why he practiced his technique so thoroughly, he could place every ounce of his energy into his punches along with using his dash to accelerate and rotate into his punches to give off more force. Ali didn't have to do that, he was 6 ft 3 while Mike Tyson was 5 ft 10.
The average height relative to their years in the sport: https://boxrec.com/forum/viewtopic.php?t=199245
If Mike Tyson didn't work out like he did (a worse engine with more horsepower) vs how Ali worked out (a better engine with less horsepower) they wouldn't be nearly as good as they were. Their training was also different.
https://therippedathlete.com/train-old-school-muhammad-alis-training-routine/ - Ali focused more on stamina than Mike did.
https://www.fortisfight.com/mike-tysons-training-routine-diet-plan/ - Mike focused on building his speed and power rather than his stamina.
Lastly, I don't care who can win but this puts in perspective the fighting skills associated with these two: https://bleacherreport.com/articles/582929-mike-tyson-versus-muhammad-alian-in-depth-analysis-of-who-would-really-win
If Tyson didn't keep up his proper training he often lost or gassed when people could outlast him. He was fast because he built up his dashes to be a weapon, he focused on his fast-twitch muscles while Ali didn't need to and did things like 6 mile runs to keep up his stamina. Ali also had a larger wingspan to boot, so he didn't have to worry about being clipped as much as Tyson did.
The point is, the more mass you have, the less stamina you may have if you're focusing on speed, that's why bulkier guys in boxing are usually Brawlers because smaller guys tend to be outboxers because they're more difficult to hit due to their speed and they build their hand-eye coordination and speed.
Which is probably what Carlos has done. As seen with his training, he did bulk himself up to deal with heavyweights, so you can't say "well, the mangaka doesn't know what he's talking about". It's just that Carlos would rather focus on his speed from where he started than to focus on his musculature.
