Author here.

Facebook does not really allow you to specify that one post should only be sent to a specific group of people (like this should only be visible to my family, this should only be visible by close friends), the functionality is hidden, it's not end-to-end encrypted, and it expects you to specify manually the list of recipient each time if it's something other than just "all friends".

Facebook also shows you everything in a feed (with algorithmic ordering to make everything worse), instead of sending you to the user's feed so that you can have all the context.