LOL off course it matters. You take the mental advantage on your opponent and that helps alot. I would not say anything if everyone was using it but there it is still an advantage even if this is not an as big advantage as something like an autoblock or an auto chamber.
I mean it's not that much of an advantage anyways. If I stab someone twice, I know he's going to be low, I don't need a mod for that. I can understand how it can make a bit more of a difference in native, but it really doesn't change much for NW.
All of the russians use it, noone cares.
my bad i forgot nobody cares about cheating in this module
IMO roughly knowing someone's health, aka saying "hes low" is enough to give that mental advantage already. It can even be a disadvantage sometimes, when people go overzealous and focus in on the low guy, thereby losing the round.