Many people I know find bouldering grades very frustrating, as an observation, for various reasons.
Bouldering grades are all over the place (except at the higher end maybe, where they are forensically and painstakingly analysed), but I think to some extent this is because something that has only a few moves inevitably highlights differences in physique and relative strengths more than on longer routes, which unless they are quite niche in style or cruxy tend to iron out to a more even consensus. Also sometimes they're just wrong, obvs.