I too was a little confused about that, but figured he knew more about it than I. The Reignheitsgebot was a law in Bavaria, which is pretty far from Belgium... but who knows.
You're all right, of course, that this isn't a witbier per se. I just like the pun. The history on the side is as accurate as quick research can get - although obviously only a thumbnail sketch - and is more applicable to the yeast I'm using than the title I used.