I think it could be a fair use of the word. In all my years following the sport, this might actually be the first time I’ve seen anyone talk about him having great posing. People talk about his mass, his genetics, some call him the GOAT of the mass monster era, but I never see anyone talk about his posing. Also, winning the show seems like a moot point, since most shows don’t even consider the solo posing routine as part of the scoring.
Compare with Kai, where most of the dialogue is about him having the best posing routines of his era (either that, or about grapefruits).
So, if one believes that Ronnie was one of the greats at posing, then it would be fair to consider his posing underrated.