Yes, it is a login process and there has to be one somewhere under the hood. Whatever the scheme is - at some point, one has to authenticate.
The trick is, you set it up once and then your user agent does it for you, so all you have to do is set up sync (or any other option) once then never bother but just hit the "okay, log me in here" buttons, optionally, choosing an identity (certificate) if you have many.
The trick is, you set it up once and then your user agent does it for you, so all you have to do is set up sync (or any other option) once then never bother but just hit the "okay, log me in here" buttons, optionally, choosing an identity (certificate) if you have many.