The flex plate makes it 1000x easier to remove the print, but I had an issue with it coming off the magnet a tiny bit when pulling off the FEP and sliding laterally a bit causing layer shift. It needs some little 90⁰ tabs on the sides to keep it aligned with the plate.
Idk what this guy is using, but I've installed wham bam flex plates on 2 large resin printers and I consider it almost a requirement. It makes print removal super easy and installation is real easy.