And you would be half correct.
The difference between a star and a superstar is preceisely the difference between a guy with one great skill, and a guy with one great skill and many good ones. So yes, the extra versatility is often what puts the superstars into a class all their own.
But there is no and has never been a superstar who's "great skill" was versatility. As a primary attribute that's for the roleplayers and 6th men. Kobe is a tremendous scorer...and he does everything else. Duncan is...well you pick it. A tremendous defender, tremendous rebounder, great post player. Green is not a great scorer, an decent rebounder...in college, he's not great off the dribble, his range is suspect, and his post game is ok, but mostly against smaller players. He might be able to take advantage of a pronounced weakness in an opponent, but he's got virtually nothing that currently looks like he'll be able to force his will upon an opponent at the next level.
What he does well is think the game and pass, he's a pretty good finisher, and he's a solid defender. That resume screams support player. And he's older than the other SF prospects in the draft (Brewer aside, who does have the one great calling card of defense), and so likely is closer to done developing.