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.