Of course, someone holding a gun to your head like that means they have no training.
Anyone with training would stand at the very least four feet away from their captive – too far away for them to rush or knock their arm aside.
In reality, if someone trained wants to kill you, they will. You will never see the weapon until it is too late. People trained to kill are also trained to never show the weapon until the very last moment.
No one with training goes running around like in movies waving a gun. Or a knife.
Life isn’t a fantasy. If someone trained is targeting you and wants to kill you, they probably will easily. Simple as that.
In every other situation, having a gun only hurts you.