Where did you get that from? BM's crew are literally her offsprings, they should be the last crew to accuse others about riding on their captain's accomplishments. Even Kaido's bounty is barely above Big Mom's, so the idea that his reputation helps his underlings inflate their bounties more than BM does for her own children is plain nonsense.
Kinemon never tanked Kaido's attack. He's barely alive after Kaido's hit, and this is a fight Kinemon can't afford to lose, unlike Ulti. Pero can be as strong as Jack for all I care, but it won't be because of his bounty. I actually think it makes more sense for Pero and Snack to be above F6 because the rest of BM's veterans as well as their top 3 are weaker than their counterparts from Kaido's crew.