I'm not sure why you changed the narrative, your pulling impulse filters are diluting the message and language. Also, anchoring is not a not to be taken literally. Coach Kredich describes holding water with the entire forearm - lateral movement causes water to spill (off the arm) resulting in *added* slippage. As he positions the swimmer in max grip and leverage in front - he demonstrated how poor head-spine alignment and an arched back affects the low side arm leverage and grip - and then corrects the swimmer's position (head-pine, tuck pelvis). Also the position of the low-side arm just past the below button where leverage slips away from a vertical position to the release off the hip. Isolating that zone on the trainer so the swimmer can feel where max/grip and leverage are. And how much a slight change in position can change that zone. The zone is very short, poor body position will make it even shorter.
What I admire about Coach Kredich is his curiosity and ability to look at any stroke with fresh eyes, removing traditional filters on how he was coached and learned swimming over the years. Also, coming up with the forearm bands on the Vasa Trainer is a great idea. putting the pressure point nearer the fulcrum (shoulder) on forearm and not on the palm to help train the whole arm hold and not just a pulling palm/paddle. I'm not sure if this was his idea, or Coach Boomer's or another coach - but gives a whole new use and context when using the Vasa Trainer. I suspect the folks at Vasa were very happy with added use case as well as getting an endorsement and plug from a couple of the best coaches in the country.