Am I the only one who thinks of these things?

Actually, this is a good point. Theoretically he should have a string bean body with almost no muscles whatsoever

It's swole from the energy retained from a yellow sun

Because fuck you that's why. He's a super hero with X-ray vision and laser eyes deal with it

*Human* muscle growth

He get his energy from the sun, that's why
Have you seen him when he's put away from it ? He's like a ficello

He's pulled planets out of their gravitational field before.

Supermans growth is dependent on the sun. They showed in Flashpoint Paradox where Clark was found by the government first when he landed and locked in a vault. He was a skinny little dude in there. He also accidentally shredded a battalion of soldiers with his laser eyes because he didnt know they did that *shrugs*

That must be why one-punch man isn't all ripped.

Regular humans also get their energy from the sun, but indirectly.