Just one data point here, but my personal experience doesn't really agree with that hypothesis. I met my SO in college but aside from their family I do not have regular contact with anyone else I met during that time of my life. I was a commuter student but I went out of my way to meet and hang out with other students.

I was lucky enough to have met my two current best friends in elementary/middle school and reconnect with them during high school. My closest friends right now are my high school friend group and my coworkers.