I remember seeing an interview (or a documentary,can't remember which) in which the subject of medical personnel during WWII was discussed.At least one person (a WWII vet,IIRC) said that on the whole the Germans respected the red cross on helmets,vehicles and uniforms...including on the battlefield.OTOH,it was said that the Japanese specifically targeted Navy Corpsmen and Army Medics on the battlefield.
Speaking in general terms I can say categorically that in my travels over the years (First World *and* Third World) I've learned that not all cultures are the same *and* that not all cultures are *equal*.
I believe the same was true of the North Vietnamese and Viet Cong.
They considered the medic armband a target.