It's probably also worth mentioning that compared to most of human history, public schooling is an extraordinarily odd social situation: very rarely would you have large numbers of age-matched children all doing the same thing at the same time, and interacting primarily with each other. Of course, regardless of setting, people may seek similar-aged friends who share interests and skill levels, but the near-exclusive restriction of friendship to a same-age peer group is what is historically unusual.

So while I agree that if homeschooling increases isolation, it could cause impaired social and emotional development, I don't think we can assume that just because it is very common, the social and emotional development of group-schooled children is not also impaired in its own way.

In particular, children in age-matched group schooling tend to have impairments in interacting with children who are younger than them, older than them, and with adults. (Unsurprisingly--they get very little practice.) There are also damaging social dynamics, like bullying, that are exacerbated by the nature of the age monoculture.