I found a serious issue with this feature - if you enable it, any accounts that were not created using an email address that can be verified by a social login will not be able to login.
For example, if I create an account with example@gmail.com, enable Google login, and then uncheck enable local logins, I can login using Google. But, if I create an account with example@domain.com and uncheck enable local logins, that user is rendered useless. Would it be possible for the next release to include the option to enable local signups, but still have an active login field?