You are absolutely correct. There are two types of players in sports. The first are those who work on skills they excell at because it's easy and they like it. They'd rather dipsy-doodle dangling drills at the end of practice than anything else.
Then there are those who work on skills they lack, because it's hard and they want to be the best at everything. They are taking 100 faceoffs with an asst. dropping the puck because they didn't get it right the first hundred times. They are the ones working on footwork when they have feet of lead, like Chara (not to mention Tom Brady) did in the off-season.
It doesn't matter if you are a 4th line plugger or a superstar, that is it, there are no other types, in any sport. Crazy enough, these two can be found at all levels of skill, though I posit the true superstars, not to mention overachieving pluggers, are the latter rather than the former. The latter gets you Patrice Bergeron and Sydney Crosby, not to mention Terry O'Reilly and Martin St. Louis. The former gets you Phil Kessel and Ryan Spooner.