I don't think there is much cherry picking going on here for an easier fight. This narrative that Stipe is this old man and Jon has some big advantage here is something I don't agree with. I think Jon just wants the name value of Stipe and his legacy and the pay day.
Stipe has 24 fights, Jon has 29, Stipe started in 2010 and Jon in 2008, so in terms of career and wear, they are very similar. Stipe actually has less fights, and less fight time. Jon is 5 years younger than Stipe, but more fights and fight time. And Jon hit his peak faster, he was doing all title fights from 2011 to 2016 while Stipe was moving up the ranks getting quick and dominant wins.
Both guys have been pretty inactive with 2 fights since 2020. Stipe got KO'd vs Francis, so did everyone else but prior to that had two wins over Cormier where both guys looked older. But Jon on the other didn't look so great vs Reyes and Santos. He did have a great finish vs Gane, but that fight lasted less than 2 mins, we don't know what kind of shape Jon is in.
I will say Jon being 5 years younger at this stage and having fought lately gives him an advantage, but I don't think it's that much. I think Jon and Stipe are both in pretty much the similar shape in terms of their prime and condition, both are passed it IMO. I don't think Jon many advantages here in that aspect.