Using platform configs at cook time

When running the cooker I’m having problems making use of any platform specific config values. Are only the windows config files read when running the cooker?
Ideally I’d like to be able to have a config setting in one of the XBoxOne config files that gets read that allows me to remove the top LOD of a static mesh so that it doesn’t make it in to the cooked data for that platform.
I could make a CVar that is something like r.XboxOneRemoveTopLOD in the default engine config file and then check the Target platform at cook time but that seems a bit convoluted (I need to change code if we suddenly decide we want the same change for PS4 for example).
I’ve tried <Platform>Engine.ini and the appropriate <Platform> Device Profile Chunk in DefaultDeviceProfiles.ini to no avail…

Am I missing something?