Company (Airbus and Boeing) Ops Manual rule...fail passive.. (Boeing CAT IIIA)...total autopilot failure in the flare visual reference achieved....manual landing specifically mentioned as being allowed if commander thinks manual landing is safest option.....
Fail operational (Boeing CAT 3B, min RVR 75m) ..for a total autopilot failure in the flare aircraft QRH says go around required...but with a caveat that refers back to Ops manual rule stated above.........
(FWIW our latest recurrent check just happens to throw this scenario in, with all the associated noises, as part of the LVOPS renewal section right at the end of a IIIB approach with visual not achieved....oh how we laughed....or not....)