Layout automatically switches to "vertical" when overriding

I am creating an template override, by removing the login just as your example. As soon i copy the file default_login.php to my owerride location i have created ( no modifications to the file made yet ) the layout switches to vertical in frontend, even if it is set to horizontal & (Payplans 3x template) in backend. Just by removing the file, things goes back to normal, e g horizontal just as set in admin.