The way I think abut this is that the characters aren't unemotional, unfeeling mechanical robots. When two different character raise a gun to another's head and makes a threat, those are not physically identical, indistinguishable situations.
Are you actually, fully committed to shooting this guy in the face? If yes and you have hard+2 your eyes are full of cold grim purpose. Everyone has seen you in battle, they've seen how you calmly dispatch your enemies in the heat of battle. They know that look, it's the last look some of your enemies ever saw.
If you're not ready to kill this guy, you're just not in that mood. You're physically more relaxed, your eyes are softer and your gaze isn't quite as fixed. You're trying to put on your grimace of determination, but really it looks more like your smile when you show your favourite guns to some of the hardhold's kids. You like to make out how big and tough you are, but everyone knows there's a human being somewhere inside that body armour.
So people aren't made of stone. You can read a person's commitment and mood from their stance, look, tone of voice and a thousand tell tale signs.
So no, making a threat and making a promise are not the same thing. They're really not the same physical act because there's more to it than raising an arm and speaking some words.