I honestly think smaller more stable groups are going to yield stronger relationships than ones that are continuously growing.

I've been on reddit for ~12 years, for example, and after five or six years still hadn't really cultivated any kind of 'group' or relationship with anyone, so I just started rotating my accounts regularly because the social aspect of the platform is essentially of zero value. HN feels much more like a community, and some of the forums I frequent are even more so, despite being largely undiscoverable and frosty to newcomers.

Does that same process not naturally play out as kids turn into adults? (e.g. college freshmen massive friend groups -> 10 years later only really talk / hang out with 10 or so folks)

I'm responding to this comment as a response to all the comments which all seem to have a similar tone. I think it's important to remember that kids are at a different stage in their life than adults. Having small locked in social groups from a young age is bad: it limits experiences, creates echo chambers, and ultimately can lead to stunted growth. The most important thing about what you said re: kids turning into adults is that they had the chance to select their 10 or so folks from a massive friend group. Locking in a social group when your choices up to that point in life are the people you went to elementary school with is likely to have severe consequences, and that is the real harm of shutting in-person schooling down.

I won't even touch on the idea/harm of replacing physical connections with purely online ones. A lot of my friends are people I have met via the internet, but our friendships have often been cemented by eventually meeting up in person. I suspect the same is true for most people who talk about their extensive online social graph.

Not to my experience. Whether big (subreddits, HN) or small (bunch of friends over a Telegram/WhatsApp chat), the groups tend to be somewhat inclusive and grow over time; the larger they are, the faster they grow. But even if they didn't, arguably exclusivity is a feature.

That's not my experience at all. My online social circle has grown substantially over the pandemic and there's several people I was only acquaintances with previously that I've grown to know much better.

Do you have a source for that?

That's also common in meatspace.