The Time Chojin have appeared before in Kinnikuman Nisei, well, the sequel that never got adapted into anime, haven't read everything because it hasn't been fully translated, but the Time Chojin there were portrayed as mutants that spawned from Brutal Chojin, made their own civilization away from everyone else, and had the power to travel back in time only once, and accelerate their healing or even go forwards in time a second or two.
There were only 3 left because 2 of them decided they were the only true Time Chojin and commited genocide on all but a kid that went backwards in time to the time of the old Idol Chojin, Chaos Avenir, who died before Nisei started, he's the guy with the Kinnikuman Great mask saying he will make things right this time.
Anyways, Mantaro and Kevin Mask defeat the two evil Time Chojin in a tag team match after they constantly kept healing and afterwards they become old men and are starting to die, they were hoping to use an item that heals everything afterwards that was introduced in the Nisei sequel because the power is risky, it takes a lot of energy and years off their life, and they used it so much that after the fight they couldn't survive.
Kinnikuman Phoenix was watching the fight and he saw the flaw way before the fight ended, he was watching them healing and thinking it was a good power but it's price was too steep, so unless these Time Chojin are different...which they may be since these aren't mutants but created by the Time God himself, it may be that the same flaw is present, it costs a lot of energy and has a harmful impact on their health, once or twice...maybe it's fine even if they shave off years of their life away, more than that and it's asking for death after the fight ends.
Also, i guess they keep their power to go back in time once since Mariposa realizes the old temples seemingly belonged to them, i guess some went back in time to form a civilization and prepare things for the future "Universal extinction" part...and i guess to justify Nisei's sequel, some decided they didn't really want to follow the Time God's ideals, and made their own separate civilization, told their kids some BS about being mutants and tried to live their lives before two of them decided to wipe everyone and one kid went to Kinnikuman's time.
Mantaro finds things about Chaos Avenir and even finds his grave in the sequel, from what i saw, Chaos was from the future and his dad would tell him stories about the Idol Chojin, about the great Kinniku Suguru, Terryman and others so when he went back in time to escape death, he wished to go back to the 80's and be in the safest time possible, the one where his heroes were around and he could be around to watch all their matches, even getting Kinnikuman Great's mask when it fell down as he was watching the events, but before Nisei starts, he went down fighting a large group of Demon and Perfect Chojin that were attacking people and died, they made a big deal about learning about him since he was a Time Chojin too.
I guess in this timeline, he will get to not die to an army or large group of enemies and get to join his childhood heroes in fighting...well, Time Chojin like himself.