[thaumasiotes]

The restriction isn't on them seeing your posts. It's on you seeing their posts. If you don't want them to see your posts, Twitter provides that functionality too. It just isn't called "blocking".

[fwip]

What's Twitter call it?

[thaumasiotes]

It's called protecting your account. A protected account can only be viewed by followers, and followers have to be approved by the account.

https://help.x.com/en/safety-and-security/public-and-protect...

https://help.x.com/en/safety-and-security/how-to-make-x-priv...

(Note that, because it's always possible to create new Twitter accounts, a whitelist is the only way to prevent someone from seeing your posts.)