Yeah, I agree on wanting to see the fun, kid-side of these two characters. I like their best friends antics in Super Sons and the few other crossovers I’ve read. I actually think Damian aged too quickly too. I liked him more firmly on the kid side, although his enthusiasm and arrogance over turning 13 (finally a teen for the Teen Titans!) was amusing.
As for romantic inclinations, I’ve seen Damian specifically show interest in girls, but haven’t really seen anything definitive from Jon before this picture. However, I also don’t reliably follow their separate adventures (Teen Titans, Superman, Legion) and have read very little with teen Jon in it.
Since Jon did actually age at a normal pace from his experience (and how I interpreted the explanation), is the main concern for a Jon romance based on the ‘what if’ scenario of him reverting to a kid, or just that the age jump for readers (and some creators, as mentioned) can be jarring, since Jon pretty much grew up overnight and in a pseudo-vacuum from our POV?