The following devices are end-of-life, no longer receive firmware or most driver security updates and receive extended support from GrapheneOS as part of the main releases with all GrapheneOS changes including all of the latest Android Open Source Project changes:
That sounds like a reasonable position. Google would have an advantage in getting timely AOSP and security updates, but getting that stuff done should be a high priority for all manufacturers anyway. As for the rest of the list, there are things I don't know about - but at a glance it looks fair enough. So I guess there could and probably should be other phones trying to meet those conditions.