let me state it as clearly as i can, to the risk of being blunt.
Meta harverst and sell your data, anyone who wants this data can certainly buy it from hem.
The fediverse spread your data, -- anything you post publicly -- around, for anyone to collect, for free.
Don’t post anything sensitive on the fediverse, seriously.
If your instance doesn’t collect the thing meta does from its users, they joining the fediverse doesn’t change anything from you in that regard.