I don't know.
Back when I got into horses before Parelli was big and all this stuff I thought I knew what Natural Horsemanship was.
Now, years on, I think its much less clear. People go on about bits and spurs, but really, I don't these mean much. Natural Horsemanship people can use them, other people can use them, it's how you use it that counts not the fact that you use it. There are plenty of good rider out there that use these tools in a way that they can be softer than other riders without them. Practically 90% of people these days tend to use rope halters and long leads - regardless of how they train.
There are trainers that you wouldn't put in the category of natural horsemen, but when you really take some time and have a look at what they're doing, the essence of it often isn't that different. Different names, different looks, but usually similar concepts.
I try not to use the term "natural horsemanship" because in my mind it doesn't make sense. What we do with horses isn't natural, or instinctual, it comes from observing horses and seeing how they respond, and using this knowledge to understand and act, which any good trainer, regardless of title or discipline, does. It might look different, or seem different, but often it isn't.
Sure, there are lots of "trainers" that aren't good horsemen, and may use cruel methods, just like there are riders who do the same - but I don't think that has anything to do with doing natural horsemanship or not.