TLDR: While Fediverse won’t directly serve you ads, anonymous bad actors other than Meta can save, redistribute, and even dox you for any information you post here. Anything you post here can/will remain forever on some malicious instance that doesn’t honor deletion requests. So be careful!
It is reasonable because I can have a trust basis with my followers who are my friends/family. If a malicious instance host can just use a plugin to view follower only post, that’s not going to be expected by an average user. That’s why I posted in YSK.