You need to ask yourself why there is no kite mark or any other form of industry standard recognition for what is a potentially a dangerous device.. It's home made using a butane torch in a situation it was never intended to be used for.....being ignited in a confined airspace..... Heat control is difficult, you need several caps, they get so hot OA vaporises before you have them in the burner. It works but IMHO potentially dangerous as nothing is regulated.. It's all silver soldered, ordinary solder and plumbing joints will soon melt under the extreme heat. Thick gloves are essential to prevent burns as is full PPE masks etc..
Having said that I know of several who find it fine. I have one that has remained unused since it's initial trials a few years ago. Butane torch is now solely used for lighting smoker fuel....
Because it is a totally unregistered home made product non of the beekeeping suppliers will touch it with a bargepole.
The guy is leaving himself open to potential lawsuits should a serious accident happen to someone using one.