Yup, if you mean that someone hit by a bullet is guaranteed to stay down, then you are correct in saying that this is nonsense.
That's probably largely the fault of Hollywood more than any one person in particular, a fantasy land where people are either dropped instantly, or say something along the lines of 'It's just a flesh wound' and are perfectly fine ten minutes later!
Of course real life is a bit different and somewhere between those two is likely to be the more common occurrence, and it's also quite likely that a good number of people who get shot will just become 'fighting mad' initally, from the increased adrenaline, there are plenty of clips from all those police footage TV shows that confirm this too.
My dad actually told me a bizarre one once when he was in the Army, someone was shot just near the pelvis and they dropped dead 'instantly' with barely a trickle of blood. The guy's friend had to be physically pulled off him as he simply refused to believe his buddy was dead from such a wound. Much later it was revealed that the bullet had ricocheted off his pelvis and gone up into his ribcage where it hit a bone and shattered causing massive damage to his heart and lungs, thus killing him pretty much instantaneously.
Conversely, my mum worked with a guy years ago, who was literally shot in the head, the bullet went in his eye socket, ricocheted around the eye socket, taking his eye out, and then came back out. Needless to say, he was then blind on one side, but apart from that, suffered no other injury.
Both pretty grim tales, but they do show that all the Hollywood b*ll****, is exactly that.
Chock