As far as I’ve seen, that’s how blocking works on literally everything. You are blocking them from your view. You are not blocking their view of you. It wouldn’t matter if it worked the other way, since they could just log out and still see everything.
If you want total banishment, run a chat room or a non-public forum that can’t even be entered or read without permission.
If there was anyone else aboard NCL’s Pride of America before it left dry dock in Bremerhaven around 2004/2005 that is also on Lemmy, they’d be able to back me up. But there is a good chance everyone else who suffered with me is locked in the loony bin from having heard Radio Ga-Ga for a week.