Sorcerers don't have training. It's all intuitive for them. Commoners are also not magic in any sense. I reject that premise as it does not match up with anything D&D in any edition has ever stated.
Sorcerers do have training they just don’t have book learning before they spontaneously develop their powers, but then they train themselves to have better control, more power, and thus they level up
Edit: and any old commoner might spontaneously develop sorcerer powers, we don’t know if their great great grandparents ever had a stray encounter with a dragon or touched something they shouldn’t have, every single unnamed NPC has the spark of potential to become a class-levelled character but the vast majority never act on that potential.
I get that. When a martial character starts being able to do things that surpass what is possible, they enter the supernatural(magic) state as the reason they can do those things. They train there physically, but the ability is quasi-magical in nature.
Sure it’s magic, but it isn’t capital M magic, it’s the fundamental magic of the fantasy setting and it’s physics that allow it to happen.
A 14 year old school girl from Sacramento swam the English Channel. How well do you think she would do against Orcus?
That’s improper equivalence, the 14yr old swimming the channel is impressive in our world, a fantasy 14yr old throwing down with orcus is impressive in the fantasy world, but those two 14yr olds live in different universes which have different rules and are not measured by the same measuring stick
Unrelatedly to your post, why are we always comparing the fighter to
human limits of normal, that dwarven and elvish and tiefling fighter aren’t measured by human measures, maybe we need to start making sure we say fantasy!human when we discuss what’s possible for them because those fantasy!humans aren’t the same as us, unless there’s been a breakthrough and someone at some research centre has learned how to cast magic missile and I missed the news report.