Wouldn't it make much more sense if he had to edit each and every one of those pony vectors in Photoshop first before tossing them into Premiere?
Well of course. I don't think you can even cut them out properly in Premier without isolating the backgrounds, which would be impossible without putting them into Photoshop first. But if you bothered to do that, it would be MUCH easier to just cut them all out in Photoshop before throwing them into Premier. Cutting things out from their backgrounds is usually very difficult and time consuming. The simple animation of MLP:FiM makes it easier, but no automatic program is going to be able to it.