I don't think there was some grand concerted effort to self-promote by the WDT guy, it's just a legitimately helpful and (at the time) novel technique for getting decently even flow when using cheap(er) home coffee grinders. It requires like 5 seconds of time and something like a toothpick or cake tester. This is not the same as the audiophile magic cables or whatever, the results are measurable and replicable by anyone with a toothpick and a home espresso setup.