Hmm,
No idea how accurate that is - know nothing about anything, please take it into consideration - but I think this may be the case: the instance show every post from every federated instances that are subscribed by people in the instance?
If you’re on europe.pub and you subscribe to “!flippanarchy” than all people on europe.pub will gain the ability to see their post in the “all”. Until at least one person do it, it’s only “potentially” connected.
Could it be the case here?
That’s what I heard, but, again, it’s all confusing to me as well :)