Please be advised that currently this feature does not work.
Could you add a reproduction path for the "not working"?
Because when I test it, it seems to be working just fine.
This feature has never worked for me, no matter what I do I can't restrict anyone from visiting my tables. Here's what I did just last night to verify that it still doesn't work:
1. Opened up a new window, clicked "Login"
2. Clicked on "New Table"
3. Clicked on "Create Table"
4. Clicked on "Advanced Options"
5. on the dropdown menu next to "Allow spectators" I change it to "no"
I then let this sit overnight, and this morning when I looked the chat log is full of 23 people joining and leaving my table, some of them wondering if I'm there or not.
I would like the ability to playtest kingdoms with people online (or even bots) that I plan to use for my IRL tournaments without risk of my friends joining the table and seeing them, but I've never been able to do that. I've tried the "friends only" option and that doesn't seem to work, but I haven't re-tested that in a couple of days, I think there was a release since then.