^^^^
Yes, I have had warranty claims via my VW dealer which have been successful.
But sure, a
BRAKE failure is not going to be honoured under warranty if you're not using oem
brake fluid. However, my understanding was that the learned gentleman who goes under the name of T_T was claiming that most other fluids shouldn't be used. No matter, it's somewhat academic and I can't be arsed to go into all the detail right now.
Re the "racing company's opinion" - AP Racing (they were called Lockheed for many years) have been designing and making brakes for both car manufacturers and international motorsport for a great many decades. I value their opinions more than one bod on the internet.