The third step, burnishing the edge, at a slight angle towards the face “turns the burr upwards”. The SEM clearly shows a blade-like bevel has been formed, perpendicular to the card face. However, rather than simply turning the burr, metal has been reformed, and the burr has buckled rather than rotating. Additionally, the burnishing rod has honed the side of the bevel, removing metal just as a honing rod removes metal to restore a knife edge.
I've been struggling to sharpen my card scraper, and was happily surprised to see that scienceofsharp.com has an article (from 2019) that helps visualize the burr structure.
Once you understand the mechanics it does make the process and assessment of the result make more sense, but it still feels luck based to me.
I have found that sharpening is a personal thing. You have to try stuff and see what works for you. I see a lot of old timers talking about sharpening card scrapers by burnishing the flats to push a burr up vertically, and then burnishing the top to roll them over into a hook. I've never not once made that work, but I've gotten suitable edges burnishing top straight away. Shrug emoji.