This is my understanding as well, after using a number of different instances over the last few months.

I believe this issue will mostly sort itself out in the future as the federated network becomes more “connected”

A new instance connecting to an existing one will have content from the established instance missing, but as time goes on that content becomes a smaller portion of the overall content.

I anticipate some development on this issue in the near future anyway, perhaps cached content that is able to be “pushed” to a requesting instance.