Spamming is the trivial way to manipulate chronological feeds. It is so bad that they need active moderation or ranking to prevent a board from going into a state of absolute uselessness.
I haven't used Facebook in 15 years, but I don't recall spam being a problem. I saw my friend's posts and replies by people who are friends with my friend.
That model may not work with all social media, but as far as I remember it worked for Facebook.