New York State's definition of a gravity knife has been limited, by case-law precedent, to include only knives which open to a locked positions "with a simple flick of the wrist". The example given by the court was, IIRC, the motion used in dealing playing cards. While it would be nice if there was no restriction at all, to my mind that defininition is about as clear and as reasonable as one could hope for. So, outside of NYC at least, getting convicted of carrying one in New York is easily avoided by not carrying knives that are sloppy loose. Getting arrested for carrying one is another matter, police officers do not always interpret the law in the same way as the courts. But that is a universal truth, not one limited to either knife-related issues or to one locale.
Can't see that having any organization come up with their own private definition of a gravity knife would have any impact at all on how courts interpret their state's or locality's proscriptions on them.