Thats a very fair point. My mistake was, that when I say “talk to each other”, my brain implicitly says “talk via text over messages”. Even then omemo is not universally supported yet, I think, so, encrypted messages can also be hit or miss.

But in OP’s case, this still kind of works, in the sense of, it doesn’t matter which instance of movim they and their friends are on, they will still be able to intercommunicate, right?