Controllers sub directory have identical controller

    is this a bug ??
I have a controller sub-directory named registrar and also i have a controller named Registrar.php
Whenever i access the sub directory registrar and have a Registration.php i encounter a Page not Found ..

example :: http://localhost/registrar/registration/register...

But when i access the Registrar.php
like :: http://localhost/registrar/method .. it is ok..

But when i renamed the registrar folder it works..

I just want to confirmed if it is a bug...

Sample directory above...