Users are able to Self-Sign Up on Instances with Self-Sign Up Deactivated

Summary

Users are able to Self-Sign Up on Instances with Self-Sign Up Deactivated

Description

Administrators are receiving notifications for new users requesting access on instances with Self-Sign Up deactivated.
It also seems to be affecting instances with "Any account with one of the following email address domains can sign up" - Instead of filtering requests from that domain only, it lets anyone from any domain to sign up.

Steps to Reproduce

1. On an instance, disable the "Self Sign Up""
2. Access the instance from another account - which doesn't have access to that instance

Expected Results

You should get a message stating that you don't have access to that site.

Actual Results

You see the button "Request Access" and by clicking on it, all administrators get a message stating that you've requested access.