I think we more or less agree, but the properties here differ and there's room for more than one solution. For example - What you linked seems good but can't work for large groups at first glance (it also suffers from much more severe comms patterns analysis attacks).

Modifying the invite link to ping a coordinator for the final channel info (I.e. accept the invite) is easy to do and would eliminate the threat you outline. There might be other options like adding a password.

I don't object to the analysis so much as dismissing the entire approach as unsound. I'm advocating for constructive collaboration. (And I've got no dog in this fight, I'd love to work on this but I'm too busy with my other projects right now).