Ah, okay. When you said graduate certificate I was thinking of something with three to six courses. This thing is a little different. (It's still $600 though, which for some is non-trivial.) Maybe not, but you can usually include them with your application, and they definitely at least care whether you've taught online before or not because it shows whether or not you know the drill. Basically, they want instructors who can jump in and do the job right away because it minimizes the work they have to do to get instructors up to speed and lowers the risk those instructors are unsuitable.