Haha, it's not about playing it a certain way, it's about sounding a certain way. If you try both those things, you will realize that there is a subtle difference in how the riffs in that song sound when played with alternate picking and when played solely with down-strokes. It is a subtle difference, but it's kinda essential if you wanna get that steady, blood-pumping rhythm that Master has.
True. And it's not even a subtle difference either. It is very, very noticeable.