Graduating at the top of your class in any primary or secondary schooling is hardly going to impress me. Some of the dumbest people I know had the best grades and some deceptively intelligent people had the worst grades. I still remember in HS some straight-A girl asking me if 23 was a good ASVAB score. Maybe if you're school is infamously conceptive, I'd think different, but I'm more interested in what someone does outside grades. Meanwhile, I knew a guy that would always come to school high as shit, acted like a class clown and had the worst grades, but was surpsingly smart. If you were to look at this guy, you'd probably assume he had no real options for a future, but I was talking to him once and discovered he was a game developer in his free time and had made some petty neat games.

Just a form of dyslexia maybe?

Why can't the man just be bad at spelling?

Because it'd be totally weird for someone with otherwise high intelligence to "just be bad" at something basically everyone else with normal+ intelligence is good at. Like, you wouldn't expect there to be an explanation? What does "just" even mean here?

He can, but if we ask why and we find out it's for the same reason a bunch of other people are bad at spelling and the common name is 'dyslexia' then maybe that's a good word to explain why he's bad at spelling?

Being naturally bad at something isn't magic, there is a reason and mechanism

Same as being naturally good at something, there is a mechanism