“you pretty much do not know what you are talking about.”
I write iPad apps for a living. Last job I used Linux for cross compiling to ARM processors with g++. I was just like your son, programming from age 10. A kid has the time and inclination to work thru all the obscure incantations needed to make Linux work. I’ve hacked Minix, the precursor to Linux. I have every qualification you could demand.
And I can say without question that Linux is still not ready for most general users. Much better than it was, but still full of “oh, oops, you just need to do this obscure incantation...” which stops most people.
The real test of usability isn’t your 9yo boy, it’s his 59yo grandmother.
You misunderstand—My kid doesn’t program. He plays music. He is not technical.