Per this link we can see there are some more on the linked than the allowed tab, these were ones that we may have federated with in the past or are no longer in operation. It is possible that some of hexbear's posts/comments are sent to a linked instance but if they are not on our allow list we do not receive their posts/comments even those made in hexbear communities or posts.
A blocked instance neither receives any of hexbear's federated information nor do we receive any of theirs.
I hope that makes it a bit more clear, most lemmy instances use a block-list therefore every single federated instance that is created could connect to it if the effort is put forth, however with our allow-list Hexbear admins must specifically add a new instance to the list for federation to occur.
Amazing, thank you for you work!