stuff like this only make it weirder for the MC to be B-rank while the rest get to be promoted, unless the "hero" did something underhanded so MC can't promote
Well, unless promotions are also based on skills, which it seems to be. (And skills measure over all power). Everything usually has a set standard so even if the MC put on a lot of effort as a skill less support, it's stuff that the party should have the brains to do anyway (like strategies and understand team composition and such).
It's just I doubt they do annual tests to make sure all party members (especially the leader) aren't brain dead chimps.
Not to mention without proof Chris can just lie about contributions or exaggerate if it wasn't intentional. After all, the loudest and flashy-est is often the main hero.