[layman]
It seems bizarre to me that in a highly automated environment such as the avionics on a modern airliner we are feeding different radalt values into different systems, allowing them the opportunity to make decisions on the same manoeuvre based on different height data.
Can systems be designed so that both radalts feed into the same system and that a single height is derived from that data? After all, the aircraft only has one height AGL. Comparisons can be done based on the individual values within set tolerances and any mismatch flagged to the crew or to systems so that the feed from a faulty source can be eliminated. All aircraft systems are then singing from the same song-sheet, as it were.
[/layman]