You can use the ROG connect to flash your bios no problems at all. Doing so is flashing your BIOS via DOS and that is the ideal way of doing a BIOS flash.
And yes I am aware the guide was written for 3 series BIOS the process is however the exact same for any bios flash. Save that there will not be a management engine update. But the things the user needs to do remain the same.
To flash in BIOS (Using the EZflash2 utility or via ROG connect) requires a FAT32 formatted USB stick drive.