Diverging my eyes is very easy and painless. Crossing my eyes kinda hurts.
This is probably because I’m nearsighted and don’t use my glasses when using my phone and instead hold my phone 20cm from my face. They’re already crossed from doing that and crossing them even more is difficult.
Diverging your eyes is how magic eye posters work.
Uh, I’m also nearsighted, and I can cross my eyes just fine with or without corrective lenses. So I want to say there might be another factor in your case.