“The notion that the marine Oswald learned Russian without government supervision/training was a joke from day one.”
Why? Plenty of people learn Russian on their own.
He worked for the CIA—that is a hard fact at this point.
That means he was being trained by the CIA to learn Russian to spy on the Russians.
Then—surprise, surprise—he went to Russia as ordered by the CIA.
That was kind of unusual in the early 1960’s... at the peak of the Russia/USA hostilities. Most of those who self-learned Russian were still quite sympathetic in Russian/Soviet/Communist ideology.