I always learn a lot in PPRune
Mutley that makes sense, the need of the air-ground logic being the main reason for recovering the LGCIU. Also the need to preserve the green hydraulic for its EMER GEN powering role. Although it should be at least possible to retract it. In the Y+B hydraulic failure we have to extend the gear by gravity to preserve the only hydraulic remaining, but it is possible to retract it if you wish. Isn't it possible at all to retract it if need be?
my conclusions so far:
need for knowing if the gravity extension is successful (3 green)
air-ground logic for whatever systems still available that need it
green hydraulic system "preservation"