I tested this today with Xerox Global Print Driver PCL6 version 5.951.9 and I was not able to reproduce your issue. I will engage you directly to review your configuration to see what we can find.
Please let me know the driver name and version that you are attempting to use so that I can review.
I utilizing Xerox Workplace Cloud Composer to associate a print driver and driver defaults to direct print printers. I configured my default in both the General tab>Printing Preferences and in the Advanced tab>Printer defaults on my target printers. I've even tried checkin the Xerox Black and White box in the Image Options tab. I've uploaded the composer files and assigned them to the direct print printer. The printers install using the defaults and configuration I originally set on the target printers. But the only settings that doesn't transfer over is the Xerox Black and White setting. I had it set to On so that the default is B&W, but the printers that get installed get set to Color.