I agree with you that look's like Canelo's managers are aiming this fight when biev will be close to his 40s.
But even if they fought when Biev was 34, Canelo would've bet him, the Russian is way too slow, and would get hit way more often than Kovalev did, a more technical fighter in my opinion.
Beterbiev wouldn't find Canelo's head, and it would be interesting to see how many body counterpunches he could take.
on the top of that Beterbiev's chin is doubtful:
at 0:30 of the video, a left hook knocks him down and he gets up wobbling,
and at 5:50 of that video
it should also be noted that in both of the clips that you posted, he was up pretty much without a count and went on to finish both guys.
people say beterbiev has a suspect chin, but he took shots from gvozdyk without really being bothered. i think he was stunned once or twice, but never hurt... and gvozdyk is a big fucking puncher, not to mention a superb boxer in his own right.
canelo is the far better boxer, but beterbiev is a brute. his career is a masterclass in breaking people down
physically. he isn't a flashy KO artist, but he just chips away with thudding shots until his opponents simply crumble under the pressure. we see good fighters work the body all the time, but the general effect is that the opponent slows down a little bit and that gives them the chance to take the second half of the fight... with beterbiev, it seems like he doesn't just slow them down, he
breaks them. i'd expect him to get countered a lot in the first half of the fight, but continuously work the body until the same thing happens to canelo, the accumulation just piling up too high.
all this is kind of a moot point, alvarez isn't fighting him when he's 34 coming off his career defining win over gvozdyk. he's fighting him a few years later, and he will likely be too fast with his defense and counters, just like you said. i think we're in agreement about what will happen when they fight, just not what would've happened in 2019.