So among the details of the newest Kench balance patch was that they changed his passive from 2.5% Max HP to 12-60 2.5% Bonus HP.

A lot of people found this weird because the change from Max HP to Bonus HP was worth something like 15-55 anyway. So the actual number change was really small.

So why change it this way?

Well, I actually suspect the rationale was mostly about future champion balance.

See, a problem with old Tahm Kench top was he was a balance nightmare. It was really hard to change his numbers because all of his abilities interfaced with HP in unique ways. So it was really hard to nerf him early, for example, without nerfing his base stats.

As a general rule, it is much easier to balance around flat numbers then around scaling, because scaling interfaces with more systems.

So overall, I expect they moved some of his power from a percentage scaling into flat numbers so that in future balance changes they can toy with that number instead of the percent scalings.

TLDR; Expect most future changes to Kench's passive (buff or nerf) to target the flat numbers.