Indeed, but realize in our keyboarding era that there are those who don't know, and then there are those who mistype. The former didn't learn it, but the latter are affected by a type of fatigue where homophones are typed by the fingers the same way chords on the piano are remembered by the hands auntonomously.
In my own typing increasingly, I see missing suffixes, substituted homophones, and similiar errors, and I can assure you that I still rememeber the distinctitons. But, in typing, the fingers are inherently moving slower than the brain, and in some cases, much slower.
I'm sure that there is some neurological study and description out there for that lag and for how the nervous system and the brain carry on while the brain moves forward without them. It may even be related to sleep apnea and a brain operating at less than ideal efficiency.
In my own case, I am still clear, sharp, and have a better memory and recall of facts at my job than any of the rest of the team, including men half my age, so I don't thtink it is an impairment beyond the physical act of typing, as I still detect it when reading it and seeing it.