You make a good point. this is actually only relevant if you're making cat 2/3 approaches. What happens is as you said, the aircraft reverts to Direct Law when landing gear down. There is no inhibition of the RA's warnings during approach until touchdown so what you get is a Autoland degradation from for example CAT3 DUAL to CAT1 SINGLE and the autopilots will disconnect.
GPWS and Automatic callouts will also be inop so hope that the weather is good =)
But there is no LDG DIST PROC Application for this failure since it doesn't affect the aircrafts ability to fly. Just its capability for accurate landing.
You can read more about it in FCOM1 (1.34.40 P2) and FCOM3 (3.02.34 P12)
Kind Regards
Tim