Disabling SSL for a domain that had this enabled would have a lot of complications, because a 301 redirect is used from http to https. So I don't think a lot of users would do this (and keep using their site without SSL again). And it is disabled when you go to the redirect tab and then leave that tab (when SSL is disabled).
But I'll create a MR in the case we still want this ;)
The reason why I made this feature request is that I had users that disabled SSL and their sites became unreachable as they missed disabling the SSL redirect and they could not even disable it anymore as it gets hidden when SSL is unticked. The server always redirected from HTTP to the non existing https.
I understand, though it can be changed when SSL is off, e.g: ssl + SSL redir is on. Turn off SSL. Redir is still on. Open redir tab, and go back to the main tab. SSL Redir will be disabled.