Ummm... it’s obvious he doesn’t actually think it’s a good idea. It’s just a “let’s see if it can be done” thing, without implying in any way that it’s a practical solution.
As for it not working, I could have told him that before he built it. Having once, as a teenager, built a campfire so ferocious that a) we couldn’t get within 2 meters of its periphery because of radiant heat, and b) not only did not go out when it suddenly began to rain cats and dogs, but in fact did manage to prevent raindrops from hitting the center of the fire, it demonstrated that the amount of instantaneous heat output required to vaporize raindrops midflight is absolutely enormous. That dinky little flame he’s using isn’t even close to big enough.