The reason for Saitama one-shotting himself from the previous day is left a mystery on purpose. Saitama saying it's unreliable data was literally just him trying to come up with a random explanation so he finally could get Genos to fix the wall. On the other hand, it is indeed simulated versions of Saitama, and while it isn't supposed to be a legitimate explanation, Saitama himself does at the end of the day say it's just unreliable data. Regardless, Saitama being able to one-shot himself from the previous day is just speculation, and if it were true, that'd honestly just be silly, even for Saitama standards, and would mean that the Saitama who fights Garou is likely thousands of times stronger than the one who fights Boros, if not more, which is wrong for so many reasons.
Genos has absolutely no idea who or what Boros was, let alone how powerful he is. That is completely random and blatantly wrong. The only earthling who ever knew Boros was Saitama. I have no idea what he means by Genos saying that CSRC is planet level in the databook. And Genos' statements about Gouketsu are barely even reliable at all. The best I'd say is that it should place Gouketsu substantially above Carnage Kabuto, maybe even the meteor if you really wanted to be out there with it, but saying it makes Gouketsu even close to, let alone above Boros' level, is absolutely ridiculous. Not to mention, Genos doesn't actually say he thinks Saitama can't win, he says that Gouketsu's menacing "aura" of sorts reminds him of Saitama, and that he's so strong, Genos believes the only SAFE method would be to have Saitama and the S-Class team up. That isn't the same as Genos thinking Saitama can't beat him, he's saying he doesn't want to risk it.
