I do know that Rico got fritz starting on the latest build and disclosed it. Not sure on the others. Think a big part of it though was Daves Nano Tanks used it and was not sponsored to the best of my knowledge. He ran a weekly live stream for the community to jump in and ask questions and I think a lot of people tried because of him.
But for me, I have been using it over a year now. It is a good salt for the price, but most importantly, it is readily available in my area. It also mixes quickly when the water it above 70. The other thing I really like about fritz though is the 4x50 gallon bag pack. The cost is a little higher, but it insures my salt stays more "fresh". I have smaller SW tanks atm but a high water volume in the house. Because of this, humidity is a little higher than desired. Using the standard box big bag, the salt gets all crusty towards the end after making 5 gallons every week. Last, when I finally get the new tank up and running, I am building a 65-75 gallon SW holding tank. When it gets low, add water and pour in 1 50g bag, leave some powerheads on, and done.