Some admission officers are happy to see college applications with extracurriculars that take place outside of school. https://insights.collegeconfidential.com/no-school-extracurriculars
Some?
Outside of being in Marching Band in which he was the section leader, my kid had NO ECs IN school. ALL of his ECs were outside of school… and mostly church and community related. He applied to and auditioned for 8 music schools… got accepted into ALL of them. His ECs outside of school were all music and church related -State Youth/community orchestras and ensembles , playing at church, and some church related volunteer work. And he had a job. He nor I even give a thought to whether non-school related ECs were/are sufficient. Maybe it’s because they WERE mostly related to his intended major? Unlike your son, his grades are pretty sucky so I’m guessing those ECs and stellar recommendations tipped the scale. They must have, cause he got into some of the same schools (or same type) you mentioned… So I say… Outside-of-school Extracurriculars ARE, in fact, plenty sufficient !!
Most people who know anything about college admissions know already that EC’s outside of school are easily just as, if not more, important than EC’s in school. I don’t get the premise of this post.