I’m fairly new to fediverse/instances, but my understanding that these Instances are federated with each other, so they can show the same posts/communities (depending on their respective filters).
So, why does searching for communities show different results, and even show different subscriber counts for one that do appear across all results?
Is this a case of the servers just needing to sync with each other?
Thee is no sync code for remote user profiles and communities. The local server counts what it has, which is often an incomplete copy - and especially the users/subscriber numbers are not fully represented. Communities also do not automatically get discovered by a new server, a logged-in user must initiate a a search for a remote community for it to be known - and further at least 1 account has to subscribe for content to flow.