I have, most people who have done DC or Dogg Crap training have done a lot of those. They definitely work well, basically the way they do them is intended to not only stretch the fascia but also give the muscle a bit of an occlusion effect during the stretch. Definitely good stuff. There was some stuff back about 20 years ago that also went into this. It was called Spyder Stretching or something like that. Basically with that you did a set to almost failure then went directly into the weighted stretches with the weight you used for the set... WHOO!!! That was a beast too!
I definitely like the whole Fortitude Training set up. Just not easy to do in a commercial gym unless you go during major off hours.