I have never seen this done with cannabis, that is interesting. I'll say a couple things, but FYI, this is coming from fruit trees (not a euphemism, actually fruit trees) so some of it may not apply. If you are interested, I'm sure you are going to google it anyway. But they use it not only to create more trees, but some trees won't bear fruit for years, so they can get you a tree much closer to yielding fruit as the cut will be on the same genetic timeline. Other trees this technique doesn't work, e.g. apple trees (iirc).
The only problem I could forsee, he has basically handled by growing this out so long (look at that main trunk, holy cow) is that you need a fully formed outer layer, like a bark you can peel. Or something that will peel, bc if you scrape too deep it can fail. It's kind of like clones in that way, if you scrape too much off it won't work. So, supposedly, you want the bark material to prevent that. I don't know how you would do it on a cannabis plant. I've just never grown it to the point where it has bark. If you don't have a bark you can peel some people use a food peeler. If you search on line, you can find a specific one that people prefer.
If you have a local tree nursery, they have a product for it instead of using the tin foil etc. I'm not sure if they sell them actually...I see them on the trees, but not for sale? As I think about it, it would make sense that they wouldn't sell them. But you may be able to find them online. It looks similar, just not aluminum foil. I have no idea what they are even called. But it's got extremely sticky tape (extremely) on both ends, & the bubble itself is like a nylon material. I think they way (at least those ones) are designed to work is you wet them occasionally. I've only cloned/cut a tree once to try this & I don't know if it failed or not, as I gave up on it. It took a long time (very basically, I did what Seafour pictured). Anyway, that is how many nurseries make a lot of their smurfs, basically, they clone or graft them.
@SeaF0ur do you know how long that process takes to root? Like how long till vigorous growth starts to happen? It's just curiosity, I don't think I'll ever do it. I'd be really curious if he did the whole plant & left a little growth at the bottom to regenerate, which would happen faster...
I think I might try regenerating on the next round. In theory, it seems like having all those roots already developed would make things go fast...