This bothers me

In "Are You My Dad" Garnet says "There are no other Gems like Steven." and Connie says "Are you sure?" leaving the other Gems silent with unsureness (I know that's not a word but you get what I mean).

Now what's the point of having that part if Steven really is the only Gem of his kind? Nearly everything in this show foreshadows other things so we should've gotten something from it.

We probably will get something from it. It just hasn't been revealed yet.

My guess, it's a multiverse thing. Steven is the only Gem of his kind in his universe but there are infinite universes with Gems like him.