I don’t see the answer to the question I think you’re askin and I want to know the answer to so I will rephrase. Please correct it if this isn’t what you’re asking.

If I am on instance A and we federate with B but not C and B and C are federated, does instance C content show up on A if only posted on C. I assume A and C users can interact with each other and on any content posted on B but neither can interact with content posted on the other instance. Is that right?