Actually, this is incorrect.  It should read "it's a prerequisite to always have the most up-to-date definitions installed in Windows Defender Offline.  Therefore an active internet connection is required to successfully utilize Windows Defender Offline" with out-of-date definitions. (XP, NT6 - unknown)

Therefore, i would recommend that MicroSoft renames this "Rescue-CD", unless 'she' enables users to manually download on-demand updates for true offline usage from another system, regardless of OS.  This could allow valid customers to prepare a machine-specific offline rescue disk long before the need to use it, without concern of internet connectivity on the potentially "infected" machine.
End of line.