I was actually one of the first people to bring up this warning on this forum. However I will say that as I envision their intended purpose, I can absotely see why they warn against it. In any climbing belay system, part of what makes them work is that the overall system is designed to give a softer catch to the climber, from the rope itself with it’s built in stretch, even to the belay device and the reaction time for the belayer to lock off and catch the climber. If you put a hitch below the device then you take out part of that system. As i watched the video, and as I think through more and more of how and when we would lock it off, in a static application with very little chance of actual shock loading, then I feel that it would be perfectly fine to back up the device, although I personally feel it unnecessary and don’t without any issues.