The non-pro Canon's often have this too. My EOS 300X does and I find it super handy when using bulk loaded film. No matter how exacting I am I can never get exactly 35 usable exposures in a roll. It always varies slightly.
Originally Posted by Loose Gravel
My Watson loaders also expose the last frame or two when loading the cannister. With my EOS 300X the whole roll is loaded so I know exactly how many frames I have. I can then take 2 blank exposures to make sure I'm on good film. Can't do that with other camera..