Obviously without having tasted the beverages yet, I think they made a couple of key errors:
1. Not using real milk. I get the intention of wanting to make this something everybody could drink, but rice milk has a distinctly different texture and mouthfeel than dairy milk (I happen to think it’s kind of gross, but your mileage may vary!). There’s almost a gritty, granular quality, which is what I believe is causing many of the “it coats your mouth and you can’t get rid of it” reactions. There really should have been multiple options for people who can and can't have dairy.
2. Making it a thick, semi-frozen, smoothie-style concoction. Designing the beverage to be an ultra-cold liquid that is fully drinkable would, I think, have been more refreshing.