Spelling (in non phonetic languages) has nothing to do with intelligence levels - it is all to do with memory and exposure. Perhaps he never went to school, or the level of education was pathetic… or he is incredibly dyslexic. Sorry if this answer sounds harsh but I’m pissed-off at what you wrote. I know of at least one illiterate person who stands head and shoulders above the “college kids” around them. They were such an integral part of our team that were bought them speech-to-text / text-to-speech software to keep their job.
I think he was Dutch - but they do tend to speak “better” English than the English.
The difference in UK/US (amongst other first language English nations) pronunciation is something I know effects hip-hop lyricism (i.e. rapping) as different pronunciations mean some words only rhyme in your own dialect.