I have been told that this is true in MW 1.6.10 or older but not in newer versions. Is this correct? If so, I don't understand the logic in removing this functionality and would be interested in hearing why it was done.
Before sending that email, I tested it with the latest version. I tested it on a protected page, rather than restricting access to the whole wiki, but I would expect the same behaviour regardless of the method of stopping someone editing. Who told you the functionality had been removed?