I haven't researched using the liquid by product of a vermicomposting bin in the manner described in the video, so I cannot vouch for it's usefulness. I did experiment with it on an area of my lawn a few years ago and after several months I could not see any negative effects from using it on my lawn. I would not feel comfortable using it directly on my garden where it might come into contact with food that I eat.
Note: I would feel more comfortable using a Rubbermaid livestock water tank if I tried to make a similar worm bin for my use. The Rubbermaid tank like I have for my aquaponics system is made from High Density Poly-Ethylene (HDPE). It also has a threaded valve that could be used to remove any liquid that builds up within the tank. Rubbermaid stock tanks are not approved for "food grade" use, so individuals must make their own personal decisions about their suitability for use in your own food supply.
I have attempted to make a "tea" from the vermicast several times and I have applied it to my lawn using a pump sprayer. I was not able to generate it in large enough volumes efficiently to continue using it, so I did not notice any positive effects (or negative).
My personal interest started in reducing household waste and using the vermicastings as a soil amendment. I have been using the worm castings in my garden for about 5 years at this point. I have also used my army of red wigglers to vermicompost more than 1,500 lbs of household waste including newspaper, kitchen scraps, leaves, cardboard, garden waste, etc.