Another reason that desktop users with dual (DGPU + IGPU) systems my want to over-ride FB-Patchers suggested PlatformID is if you want to use your IGPU in headless mode.
Genuine desktop Mac's with dual GPU configurations such as most iMacs and some Mac Mini systems use a headless PlatformID to inform MacOS that the IGPU does not have any physical display connectors but it is still available to MacOS for IGPU hardware accelerated features such Airplay Display Mirroring and Video Encoding/Decoding (Intel Quick Sync)
Note: Systems with workstation class CPU's (Intel Xeon) do not have a IGPU as such you should not attempt to set a Headless PlatformID.
If you don't need to use a headless configuration, you can skip down to the next section titled WEG Configuration Continued.
Headless IGPU Configuration
If your primary display adaptor is a DGPU such as Nvidia or AMD and you have a supported IGPU then using a headless PlatformID will allow your Hackingtosh system to be more stable and behave much more like a genuine Mac with access to IGPU hardware accelerated features.. Use of this mode requires that the IGPU is enabled in your BIOS and that the DGPU is set as the primary display adaptor, you must also use the correct Mac System Definition (SMBIOS) that supports dual GPU configurations and matches your CPU & IGPU type.
这个说得很清楚了。