Judging by what has been said in interviews and in Jon's story in Infinite Frontier, I'm thinking it's because Jon's looking for a "anchor" beyond just his family. This is his native time and world, but he's come of age so far from the scope of it that he has to reform roots to it, and see what kind of person he wants to be here. What better place to find yourself than college (in fiction. Not in real life)?
Maybe that's why he reforms a secret identity (or at least keeps his identity on the low)? He figures "well, dad was a stranger in a strange land, and he did the whole secret identity thing to blend in and be more part of the world rather than above it, right? So, maybe that's what I should do?" But then clearly that doesn't last long.
But it's worth mentioning that the last time Taylor wrote a Superman offspring who took over for Clark and was worried about climate change, he underlined the fact that said offspring was inherently part of humanity regardless. It was through embracing that idea that said offspring was able to stand before the UN and call attention to the reality of the climate situation as a partner rather than an overseer. And sure enough, both the climate change story beat and the fact that Jon being part human links him to humanity in an inherent are plot points in Superman/Wonder Woman Future State. Jon even says that it took place early on when he was starting as Superman.
So I expect part of his journey will be relearning his inherent humanity and the responsibilities that come with it.
You're thinking along those lines too, huh? Yeah, as soon as it explained the Truth's whole deal, I remembered Taylor saying Jon would have to figure out how to fight government inactivity to climate change, and I recalled Taylor's MO in a good bit of his work, I felt like Jon would work with them eventually. Them exposing his identity for the second time is likely there to start the relationship off rocky. Basically Jon going "you're screwing up my whole plan to relearn how to be human!" But then the Truth organization likely shows him that being human comes with its own set of responsibilities, and that means rolling up your sleeves and using what ever privilege or gifts you're afforded to more directly fight our demons as a people.I’m also looking forward to what his supporting cast will look like. I think he might end up joining the Truth news organization (but hopefully in a role different from journalism).
From there I think it's possible Jon goes into sociology as a major, and becomes more activist than journalist.
I high key want to see Jon and his friends get arrested at a demonstration, and have the cops wide eyed as they slap cuffs on Superman. Because you can totally do that now since Superman now has a social security number and home address on file! Lois guest stars and comes in to bails them out/rips the cops a legal new one as she talks circles around them.