The uniqueness is that Conner isn't Superman. The idea isn't that Jon is a 17 year old who has the powers of Superman, but rather it's the fact that he's a 17 year old who has the powers AND title of Superman, and that makes a world of difference that I don't think can be understated. He's The Guy...and he's 17. He's The Guy that will be looked at to punch Darkseid in the face when everyone else is down...and he's 17. That's a pretty big deal. He's Superman at 17 standing on equal footing with Batman and the rest of the JL. What he says in the room and does in the world has the weight of SUPERMAN behind it, and how that clashing with the fact that he's 17 and a freshmen in college is fascinating.
That's just not something Conner replicates as Superboy at 17. Like, he can be on the Suicide Squad right now hanging out with questionable people, and it just doesn't mean the same thing if Clark or Jon as Superman were to do that.