Ion Auth PHP5 magic question?

[eluser]nevercode[/eluser]
I want to use Ion Auth for my backend auth, but in documentation there is something I didnt understand.

NOTE: Methods available in the model are called through the controller using PHP5 magic. You should never use ion_auth_model->method() in your applications.

so $this->ion_auth->method() , I should not use it in my admin controller with load model ion auth.
but I dont want to redirect domain.com/auth for login. if I extend my Admin controller with Ion auth like class Auth extends Admin_Controller. Will that be a problem?

or can I use auth model methods inside my admin controller?

domain/c/m

domain/admin/login (login is in admin controller)

thanks for help . thank you.