I believe they are referring to "Weiss Distribution Tool". I have a manual lever espresso machine that I used daily for a decade. The idea behind WDT is real. Distributing the grounds evenly makes much more consistent shots. If the grounds are not evenly packed, the water under pressure breaks through a channel and the shot tastes like garbage. It's not quackery, just fluid dynamics. One can argue that grounds can be distributed by other means as well. Stirring with a needle (WDT) is the quickest for me.
meh, it's arguably the most important new technique in espresso making in at least the last 20 years. I think John Weiss deserves some credit for that.
I can't believe I'm about to defend this, but unless you have an anti-static grinder spraying water does cause a lot less mess and ground coffee flying everywhere. I had to do it with my Wilfa Svart grinder (and still do when I use it) but I don't need to do it for my Niche Zero. When I use my Wilfa Svart without a spray of water (or just a droplet of water stirred in with the handle of a teaspoon) I notice the coffee is a lot messier coming out of the grounds container.
