Edit: to answer your specific quesion, no there is no chaining, it is an all-connects-to-all type of network (with the allow-list as the limiting factor). Other Fediverse (ActivityPub) software operates similarly, except that you can subscribe to any other instance (Unless on the block-list) and then that instance gets added to the instance wide allow-list of your instance automatically.

Thanks for calrifying this! now I understand :)