> They were all polite about it, but it started making me wonder if all of these other aspects of homeschooling were just a fig leaf over a whole lot of religious indoctrination. Maybe those kids are fine, I didn't quiz them, but it did raise an eyebrow.

Multiple studies show religious people are happier, healthier, and have greater civic engagement. Mormons, who you probably consider extremely “indoctrinated,” live 5-10 years longer than other whites, are tied with Jews for happiest, and have among the highest upward social mobility of anyone in the US. So those kids are probably in better shape than the public school kids.