Didn't catch that. You're right. If he were still going by Superboy, then it would make all the sense in the world to introduce himself as such because they just called his father Superman at least twice before then.
And really thinking on it, "Jon Kent, Son of Superman" as an IP is pretty recognizable. That's the name of Superman's Earth father, quick and easy to write out, and he can always fall back on the son of Superman part for extra recognition.
Side note: Did you notice that Jon apologized to Jor-El after Jor apologized to him for not talking? At first I took it as Jon getting ready to chew him out (especially with how he answered him at the start), but I read it again, and it reads more sincere. Jon's warning to his dad last issue seems to now come off more as a plea for Jor-El as well as what a mentally compromised super genius with the powers of a god might mean for, well, everyone.
Also noticed Bendis makes a point to say that Jon got a lot of reading done in that first "year"/"summer." Hope that means some cool new alien know-how to go along with his new alien slang. Plus, I noticed that Jon makes a note that basically zero Earth news not related to Superman makes it out into the galaxy. More United Planets set-up I bet.