I'd argue that based off Jurgens' words-- "Jon is the future of the Superman franchise" (I'm paraphrasing)-- he was always going to be Superman in much the same way as Miles. How you view Jurgens' words is up to you, but given the state of Superman at the time of Jon's creation and now, I don't think it was a far leap to think that DC had their eye on him being Superman in the here and now at some point.
And in terms of Jon not being able to actively represent bi kids? You're simply not going to please everyone, but you can try to cast the widest net possible, and Jon being a bi Superman as opposed to any lesser IP is for sure the widest net available to him and within his IP. In comics and pop culture the Superman name is among the biggest stages there is. So unfortunately he's not going to be able to represent the fairly specific age group you'd like, but the trade off is having a demographic see themselves in the biggest superhero on the planet.
Him being Lois and Clark's son cannot be understated, but it will always come second to the Superman name, and because of that it's not nearly on the same level of recognition as Miles as Spider-Man. Him being Lois and Clark's son legitimizes and enhances him taking over the Superman name. Remember Kenan Kong? We literally had a person of color go by Superman in the main continuity with their very own book...yet STILL didn't hit as hard as Jon taking over and coming out as bi. And similarly Jon being created got itself some attention, but only in comic circles. My mom couldn't tell you who Jon was last year. But LOIS AND CLARK'S SON BECOMES THE NEW SUPERMAN AND IS BI did the trick.
Jon brings the legitimacy by being their son, but without the name he's obscure. Add the two together and there's a chance he becomes a household name before Damian (who still has to contend with three other identical brothers and the fact that people just sort of homogenize them all together).