I don't know for sure why they would say that. Frankly I haven't had time or the energy to read the Red Cross pdf yet. If finishing my reading list is what triggers my death; I will never die.

Just a guess, but generally one of the main concern with the Red Cross is typically disease control. Corpses, contrary to popular belief, and a point likely emphasized by the RC, are not a major source of disease. Using lime to control disease from decomposing corpses is futile because corpses are not a major source of disease. The major source of disease are the infected living. Liming live people is generally frowned upon.

The benefits of lime are, in my experience, primarily aesthetic. The stench of rotting corpses is not dangerous or infectious. People used to think smells carried diseases. The term "malaria" literally means 'bad air'. Which is what they thought caused malaria. The fear of 'sewer gas' is a superstition that has survived into teh modern area.

That said foul smells are IMO not entirely secondary. The cloying smell of a rotting corpse can be literally sickening, even as they are not infectious. Also, In many ways, smells define how we feel and think.

The Red Cross is primarily concerned with keeping people alive. Lime should not be a primary concern. You wouldn't want to displace more vital supplies, food/water/medicine, with lime. That said, as individuals and families, a few sacks of lime would bring some welcome relief from the stench. Even short of dad bodies it is useful. A bit of lime regularly spread over the latrine trenches makes a big difference. A camp that smells sweet is going to be a happier camp and a less stressful environment.