Interesting, this would definitely explain these errors. Similar to there's/theirs, they're/there which are similar examples of the same. Writing out words based on such a phonetic memory would explain all that.

But the next question to wonder is whether this is English specific or person specific?

Is it that native English speakers form their language primarily through phonetic patterns and translate back to spelling from there, or is that some people simply crunch spoken language and other people crunch written language in their heads?

I definitely start from letters and words, and I'm often lost at how to pronounce something because, in English, you can't deduce pronunciation from the written form. In many cases you just have to "know". But I'm not a native speaker so can't tell if this is just because of how my brain works or because I learned English later in lafe.

I can't backreference to my native language, Finnish, either. Finnish is spoken exactly as it's written. If you know how to say a word you know how to write it, and vice versa. So the phonetic and written forms do not differ.

If anyone native to English could verify that what they keep in their head is "written English", that'd be a valuable counter-point to suggest it just depends on the person.