Spotted this wording on a well-known computer supply web site - clearly the O/S is being sold as a stand-alone with just a "hint" at being available for retail-supplied new computer builds:
Windows 10 OEM is a full version of the operating system not an upgrade. The OEM operating system is not supported by Microsoft. To acquire Windows software with support provided by Microsoft please see our full package "Retail" product. Microsoft recommends all files and programs be backed-up prior to installation.
Windows 10 OEM is intended for pre-installation on a new PC and cannot be transferred to another computer once installed. Product ships in a white envelope.