By the looks of that header file, the i965 driver covers multiple different devices, I'm guessing it's using those values to enumerate a list of the Intel CPUs

By the looks of that header file, the i965 driver covers multiple different devices, I'm guessing it's using those values to enumerate a list of the Intel CPUs that the driver works with. In terms of Wayland, I would suspect that it isn't necessary to have anything vendor specific, the whole point of targeting an abstraction layer like the DRI is to eliminate the need to cater for differences in devices.