Pixels used to be officially supported by the Android Open Source Project. Android 16 dropped Pixel support and they're now much harder to support than many other devices. We have to do a lot of reverse engineering and backport QPR1/QPR3 Pixel firmware/drivers for proper updates.
Motorola is providing official support for GrapheneOS and has multiple engineers helping us port GrapheneOS to their devices and implement the required security features. We'll have what we need provided officially and can work with them to improve driver/firmware security too.
Motorola can get Qualcomm to make improvements too. For Pixels, we regularly file issues reporting weaknesses and proposing improvements but have no special access and they often don't listen or prioritize the issues. Official support for GrapheneOS from Motorola resolves this.