Good question- Why? Well, in short the other options are not as good for this particular character and based on where we live and laws. He has found college students far easlier to connect with than high schoolers or age peers. I'm for the community college dual enrollment option.
I'm curious about EPGY experiences as well. The costs a bit high and would like some input if you have ideas on value?
Of course-- common interests.
Have you considered pairing him up with a college-aged "mentor" who can just spend time geeking out on the subject with him? That is-- you pay for a "tutor" but the reality is that they just "play" together on the topics they both find interesting.
