@Josef P.
Although you didn't say so, the read only table in your demo is saved as a system table.
Although the table itself cannot be edited directly, it can be altered using the query you so helpfully provided
Using a different approach, I have created my own demo with a standard (non-system) table which contains one field and one record.
It also contains a query & form.
The table cannot be edited directly or from either of the other 2 objects.
Records cannot be added or deleted, nor can the table be deleted.
My thanks to
@GPGeorge for the idea behind this demo
@georgevolos
I agree with the comments in previous posts. Tables are made 'secure' by ensuring users have no access to them
However, you might find the attached demo of interest