I fail to see the justification for not considering this a (super)tribe. I wouldn't think of Cat's Cradle as the authority on social dynamics, but "granfaloons" refer to people that have no connection, whereas everyone in the supertribe
is connected in a meaningful way.
What we are dealing with is a local community (for which I believe "tribe" is a perfectly valid use), which is directly and closely linked to nearby communities in such a way that, when combined with a binary and divisive choice, makes the whole network form a virtual supertribe.
With only two choices, so you are either 100% aligned or 0% aligned which makes it very difficult to have connected communities with differing opinions. Each individual is either aligned with their local community, or at risk of being ejected from it. With no connected communities of differing opinions, this in turn means you get ejected from all other possible local communities - the entire virtual supertribe. This makes it far less likely that someone will deviate than if it only affected their own direct connections.
If you had, say, 10 choices, you would be able to have a community that was only 70-90% aligned with its connected communities while still being tolerated, so no virtual supertribe would form.