Over in the NIB warranty discussion thread someone posted a link to the "original" GnR warranty, which is dated 9/20 (though the filename suggests it was still in place as of Nov. 2020): http://marketing.jerseyjackpinball.com/gnr/GNR_Manual_Nov2020.pdf
It's hard to see how playfields wouldn't be covered for 90 days under this "Bumper to Post" version of the warranty.
The current GnR warranty (dated this March, 3/21) is much less expansive and essentially mirrors the Stern approach of no written coverage for playfields.
For people that had their GnR playfield claims denied, were you discussing the "Bumper to Post" warranty with your distributor and JJP, or this new, more limited warranty? And have you considered which version of the warranty should apply if you made your deposit before the warranty terms were revised? Or if you took delivery of your machine before the warranty terms were revised?