As a self-taught SWE myself, I agree with your observations. Two of the most talented engineers I've ever met were self-taught. The interesting thing about the two people I'm thinking of is that, besides being self-taught, neither one of them actually even went to college. One of them actually dropped out of college, then went on to get hired at Netflix at 23 years old, back when they were only hiring senior engineers.

Me, I have a degree in math, but 97% of what I know is stuff I picked up either on the job, or because I found it interesting. Besides those that picked up CS as a major when it was a hot field, I'm betting that some of them get the love of tech beaten out of them by their college experience. I certainly know more than one science major who felt that way after graduating. (Not me, though. I'm weird, and I still love math just as much as I always did. Maybe even more.)