Your tip looks like the surface of the moon. Rolling leaves a denser more uniform scoring especially around the perimeter - where the pik fails.
Sorry are we still talking about pick use here...? Regardless the idea is to have a rough surface, not a necessarily a symetrical pattern. As long as the chalk transfers to the tip the practice is successful. Pick, sandpaper, shaper (as an abrasive or embossing tool) it doesn't matter. The earlier discussion was why people would opt for a pick over an abrasive. That's a material loss thing, which is not a concern for you considering the way you're using the tool.
The surface of the moon thing is byproduct of tapping. I also tap rather than roll. Rolling with any deep penetration could pry up tip material, which isn't something I would want to do.
If you had issues with a pick, that's cool. Different strokes diff folks... I have had zero failure/issue using a pick, and have tried those shapers as an abrasive in the past. When I saw that a pick embossed a rough texture into my tip without risk of removing material, I decided to go that route. I suppose I could use a shaper as you do as well... A tool meant to be an abrasive is designed as such. Pressing the texture of an abrasive into my tip would definitely work, but I think it wouldn't work as well as a tool designed for the job.
All that said..., again..., a pick can cause damage if used incorrectly. If someone opts for the tapping method like I do. It would be easy enough to bury a point into the ferrule of you weren't paying attention.