I have used this type of approach dozens of time
successfully myself. However, there is a danger with
posturing: if it doesn't work and the assailant overrides his
natural instinct to run/ freeze then you could be in trouble.
You have certainly lost the element of surprise that's for
sure. If you throw a challenge it may be met and accepted. If
it is you had better be able to back it up or be able to back
pedal in a hurry. I never throw a challenge unless I am
totally committed to following that challenge through should
it be accepted. It is fair to say that if you don't believe in
what you are saying then your potential assailant won't
believe you either.