Not sure if a scratched glass waiver will hold up in court every time. I know upholstery cleaning waivers for sofas that may bleed do not hold up in court.
If the manufacturer says dry clean only a you ignore the instructions and wet clean it you are 100% liable if the dies run.
If the glass manufacturers say DO NOT USE A SCAPER and we ignore their instructions we should be 100% liable. Conning a customer "victim" into signing a waiver absolving you of all blame when you deliberately ignored the manufacturers instructions not to use a scraper seems wrong. We are supposed to use another method. I can Understand why a judge would throw the waiver out.
Playing the devils advocate here
They've got us between a rock and a hard place because we really don't have an alternative method that yields perfect results every time like wool and razors do.
Wooling and scrapping itchy glass is VERY RISKY BUSINESS cleaner be ware.