True. The police assume the caller is being truthful, at least at first. If somebody calls and says "there's some nut in a red shirt down at Andy's parking on 12th and Crockett threatening people; he's got a gun under his shirt!" then that's what they'll look for when they arrive.The police believe the first person to call in.
I probably would have "inserted" another step: holding up my palm and saying STOP. Then the next step, if they didn't stop, would be exposing my gun and repeating it.
Normally, if nothing happened, you wouldn't call the police. But if you had to display your gun in order to stop them, that elevated it to another level. It doesn't hurt anything just to file a report. But you'd have to be very careful to NOT make it look like you pulled a gun on somebody just for asking for money.