I am not 777 licenced (and should pull my head in) but can only speculate on what I know from the 767 & 744.
That is, during an autoland if an "Autoland Critical Sensor" fails (RA being one) AND below 200ft, the ASA indication in inhibited from changing from LAND 3 until Touch down. Not sure if the EICAS " L,C,R" RA MSG will also inhibit.
Above 200ft and an autoland critical sensor fails "LAND 2" will display. I think BUZZ is confirming this on the 777.