@orenwolf It (the lack of returned email/name on subsequent log ins) did not appear to be an issue. I believe that I was able to close the sign up window and resume sign up with correct details passed in. As I stated before, I was able to log in with Apple afterwards straight away with no issue.
The only issue I faced was the CSRF error unless the site setting I mentioned above was disabled. One potential issue is the lack of a name on the sign in form and that the username is whatever is before the @ sign in the email (however if you ask me, these potential issues are either a non issue or can be easily fixed by the user).