That's the point of GrapheneOS. They've been excellent at providing fast updates and long-term support for their supported devices.
Let Motorola do the hardware and GrapheneOS the software.
GrapheneOS is fully dependant on the OEM of the phone to supply them with up to date drivers and can't support their builds longer than that.
As far as I know, only Motorola is given access to the driver source code for all the chips, which then as part of using it, they are obligated to release it, which then GrapheneOS can then access and use it.
As a result, Motorola's software support is just as important as Motorola's hardware