I remember at least in SoC there were mods to make Stalkers be able to switch off the flashlights to hide better. I haven't seen this behavior in CoC so far.
This might be a concious decission (after all, they need it to see in the night), but I believe that at least your hired companions should switch off the light during the night if you have ordered to "stay down" and in passive mode. I find impossible to go stealth if my companions are making themselves flashy during the night.
Is there any option to tweak this, or maybe due to the game engine the NPCs will see each other anyway and it's not dependent of whether they have it on or off?