If the gun in question were a double action revolver, I would say that one is accurate. The physics of the design make it so.
It would take some incredible dexterity to get your finger -RIGHT- where it needs to be, and then you'd be in quite a position to have your hand torqued to oblivion. Point is... I can't imagine this is the world's finest defensive option or position, however I would say that if you could get your finger solidly behind the trigger of a double action revolver, there's just no way the assailant will be able to discharge that revolver as long as your finger is there.