PSA: stop gluing your headbands straight to the spine, you'll lose the round

I keep seeing this in beginner bindings people post on here and it drives me up a wall, so I figured I'd say something. Last month a lady brought me a book she bound herself in her kitchen, and the headband was glued flat across the spine with what looked like wood glue, which killed the round completely. The spine had no shoulder left to speak of, and the pages flopped open past 90 degrees every time you set it down. I asked her about her setup and she said she was following a video where the guy just ran a bead along the top edge and called it done. In my experience the headband should sit on the edge of the text block so it covers the gap and gets supported by the board, not merged into the spine itself, or you lose the shape the whole thing depends on. Her book was a wedding gift for her sister too, so it stung watching it sit there all flat and sad. Anyway, if you're using a tutorial that skips the shoulder, check what it says about that step. Has anyone else run into this with a book from a craft store class or a YouTube course?