There are real medicinal properties of Japanese Knotweed. It is currently the commercially used source for resveratrol, one of the most heralded supplements for health and longevity. Just make sure that what you're eating isn't poisoned to stop its invasiveness.
I have tried to eat the stuff once and only once. it is seriously sour like rhubarb I tried the new shoots around 6 inches tall, and soaked in sugar it would probably be edible perhaps the blanching in the video gets rid of some of the sourness.
I have read that you can make the root into something like a supplement. It is a food. Perhaps it can be chopped up into small enough bits that you can add it to something bland like beans or rice and it will add needed flavor in small enough but frequent amounts.