I think what the text file meant by OEM are drives with model GWA rather than GSA. There is a GWA-4163B which comes as a drive when you buy certain systems from companies like HP. GSA and GWA drives are actually different - the GWA ones have no DVD-RAM support so the firmware is not compatible. Sometimes these GWA drives end up on the open market.
So I think you should be ok flashing your drive. The latest firmware version for the 4163B is A105, btw.