I don't think the clustering needs to be geographic; isn't NaNoWriMo based on essentially the same principle? Seeing how far along your peers are can be a useful kick up the fundament when you're lagging behind.
Never underestimate the power of the NaNo forums, or subreddits, or general forums that open a NaNo board. It's not just about pacing, it's about communication.
Online forums are great, but I wonder if they're missing something nevertheless for lack of physicality.
One of the more interesting papers I read last year was "Knitting Community: Human and Social Capital in the Early Transition into Entrepreneurship", Kim 2018 https://goo.gl/1AfwZG on knitting enthusiasts on the Ravelry knitting forums https://en.wikipedia.org/wiki/Ravelry - despite being eminently digitizable, participation in offline knitting circles still appeared to be a big predictor of knitting success & innovation.
I agree it doesn't need to be, and the Internet has really helped people get some of the benefits of these clusters without the disruption of uprooting their lives.
At the same time, we are physical beings, and there's nothing quite like the experience of sharing a space with people into what you're into.
