give access in RLS only to 2 calculated tables?

Regarding roles:

I have created 2 calculated tables, and I have one specific user that I want to give access only to those 2 calculated tables, and revoke it for any other table. How can I achieve it?

Lastly, here Row-level security (RLS) guidance in Power BI Desktop - Power BI | Microsoft Docs  it says that FALSE() doesnt allow the user to read the table and TRUE() it allows the read.  How about, for the cases that it remains blank? is that a true or false? (I ask this because of maintanibility, not sure if I have to add FALSE() again for every new table that I create in the future).