Did you know that Pleroma, a Fediverse software, has the option to make "followers only" posts that reach their instance, public on their instance if they choose?
They can also automatically deny deletion requests if they want.
It's always important to remember that there's very little privacy on the internet. If you post something, even if it may seem private, always has several ways of going public and existing forever.
Pretty much everything on the internet is public and will not be deleted on request.
Screenshots and internet archive also exist.
If you don't want your post to be seen by most people, don't post it.
You are not safe just because the software or platform you're using says you are.