Android 17 QPR1 is the first release since Android Honeycomb (3.x) adding new APIs for app developers without a release to the Android Open Source Project. The new APIs are currently exclusive to the Pixel OS and aren't available to other Android OEMs.
https://developer.android.com/sdk/api_diff/37.1/changes
That’s why I was so gutted that DivestOS shut down. It was such a good alternative to GrapheneOS and was usable on phones other than Pixel.
I guess CalyxOS is the next best thing nowadays, since it can be used on some Motorola phones, Fairphones and the ShiftPhone 8:
https://calyxos.org/install/