Hello,
If you already created an account using FB then you can log in using FB only. If you created account using Google then you can log in using Google only. You can’t mix that.
If you just create an account the first time you shold get the login to FB form and then confirmation form (I did not see that on your video because you probably have already created an account using Google and tried to log in to that account using FB that is not possible).
Regards