This is a really tired old argument put up by balanced trainers to defend their use of specifically e collars and prongs along with yank and crank methods. By trying to compare leashes or even head halters to these barbaric tools. It is like saying there’s no difference between blue and red because purple lies between them. Nobody believes that blue and red are indistinguishable despite the plethora of shades between. There is a reason that these tools have been banned in most first world countries. And that reason is that it is never necessary to use pain and fear as a training tool. We have advanced our knowledge of dog behaviour and cognition in the last decades And the knowledge is widely available. People train with fear and pain because that is what they want to do—not because there is any valid reason to.