It's a system that allows even those old systems to still use banking reliably and securely, so yeah I'd say it's an excellent system. As far as GrapheneOS goes - now that they're partnered with Motorola they might actually get some certification, along with a proper security audit from Google. Not sure what the details of the supported functionality are gonna be there.
reply> It's a system that allows even those old systems to still use banking reliably and securely
replyNo, Play Integrity labels those old systems as secure, _even though they are not secure_ due to lacking years of security patches.
Play Integrity does not prove that something is _secure_, only that the OS that is running _was approved by the phone maker_.
Older Android phones that haven't received security updates for two years are not secure. The Play Integrity check therefore does not mean that the phone is secure, but only that it is a certified smartphone that came with Google services preinstalled.
reply> It's a system that allows even those old systems to still use banking reliably and securely
replyThis is the crux of your entire argument, so you kind of need to actually substantiate it. Does Play Integrity catch an app from to Play Store using an exploit against a comically ancient vendor kernel to do anything it wants? How?