Having been around the industry I can testify that there is NO way that gait is achieved without soring of some type, and it is done by everyone. Big Lick gait equals soring.
Kerosene/diesel fuel/mustard on skin, under Saran Wrap, golf balls under pads against sole/frog, carpet tacks, glass, letting horse move for one pass and then standing so horses gets sore in the shoulders/back, and just the overall effects of standing/sitting/laying down and having to put their feet down every minute of the day in an unnatural way, also is soring too.
Those horses are in pain, same as you would be if I stuck high heels on you, rubbed your legs raw, and tied weights to your ankles and expected you to run. No way around it.
Every trainer/rider/exhibitor that shows Big Licks is showing a sored horse, and one in pain. No exceptions.