User registration settings show incorrectly as disabled when board-wide emails are disabled

Under "User registration settings" my account activation is usually set to "by admin". However, when I disable board-wide emails the account activation shows as "Disable registration". However, anyone is then allowed to register without any authentication.

I would have thought that this should show as "No activation (instant access)" rather than "Disable registration".

This has lead me to believe that the registration is automatically disabled when I disable board-wide emails. However this isn't the case as anyone can then register instantly and post to my forum, when I switch off board-wide emails.

This has led to spammers registering and posting on my forums while I thought that registration was disabled.