You're not wrong and I think I've watched most of them; I'm just about finished un-bundling 6 oz of sinew ready for 2 crossbows and a hornbow - about half of what I need, I think, but, this chap is using techniques I've never seen, or, only heard rumours of, like using backstrap (?) still in its sheath, after steeping in some kind of liquid to keep it workable. Also he boils the core in some kind of chemical bath - anyone any ideas on this one? The video is fascinating and a thorough look at horn-bow building, going through each step of the process, using all the 'normal' techniques and it really is well worth watching, but it does raise questions along the way
Using backstrap without pounding it out and splitting it up will make sure that the strip isn't saturated with glue, additionally this is inviting adhesion problems when attaching it to the core or other layers. Many things will work on weak or less stressed bows, you can get away with the wildest things. Let's ask ourselves why we will not find these "unconventional" ways anywhere else in old bowmaking manuals.
We could go on and on here, from those weird bumps to chemically weakening the stiffening plates etc.
But to get back to tradition, it's amazing how similar old techniques are across the board over a vast geographical range and timeframe, spanning from 2nd century BC Rites of Zhou to 14th century Swiss Hornbow-prod makers, to 20th century Hein's "Bogenhandwerk und Bogensport bei den Osmanen", to modern korean bowyers. There are alot more old sources that you could list here.
I'd strongly caution seeing this video as anything but a weird marketing stunt, but take it as an invitation to sharpen ones "tools" and find out more about other sources. In that sense, it can be useful.
I'm always intrigued by looking at the props of a scene. Buzzwords and materials that are on the table, that are unrelated to the workstep, what do they want to tell us with that?