Bags are not 100% handmade nowadays, some parts are machine stitched.
For example let's take the handles of a Lindy or Birkin, only the base is hand stitched, the rest is machine stitched, but of course no one would ever tell you this because they'd lose the allure of an entirely artisanal product. But if you look closely, you notice the difference in stitching.
Sellier bags are usually almost entirely handmade, retourne bags I'm not sure, but I wouldn't be surprised if the inside of the bag is
machine stitched, that's also why Sellier is more expensive than retourne.
Back to the video, I'm pretty sure that as nice and insightful as it is, it's mostly staged...