Well, the only thing I can think is, that's probably the best way to evenly moisten the product before applying. If you use a wet brush, just because of how the hairs lay, it could cause unevenness and streak on applying. This is why I never would use a wet brush with the pressed pigments - it would dry unevenly and crease and get crusty. I'd just mist my eyes with Fix+ after application, instead. Putting the Fix+ directly on the pan would be smoother, but yeah, kind of weird from a hygiene standpoint, since those p/ps feel so moist to begin with. Maybe their water content is already high enough to allow it?
I love this artist a lot too - she's her own living example of her artistry! She is absolutely gorgeous and so glam when she's done with her work.