Sharpening angle, degrees per side that is, has nothing to do with asymmetry.
No matter what angle you sharpen at, you can put the center line of the edge any where you want depending on how much grinding you do. If I sharpen at 10 degrees on the right side of a gyuto and remove metal at the edge until there is no back bevel, then the asymmetry is at something like 0/100. The edge is as far left as I can make it. Whether I do that at 10 degrees or 20 degrees, the edge ends up in the same location and the asymmetry percentage (let's call it percentage, k?
) is the same no matter what angle I used.
Now, same knife, if I sharpen the left side at 15 degrees for just a few strokes and move the edge in only slightly, the asymmetry might be at 20/80. Keep going on the left side at 15 degrees until there is no bevel on the right side and the edge bevel asymmetry is at 100/0. You could stop at any point, using any angle and have edge asymmetry (or symmetry at 50/50) anywhere from 0/100 to 100/0.
Hope that makes sense.
Also, please keep in mind I'm only talking about edge asymmetry and not entire knife grind asymmetry. Obviously sharpening at the edge can not change a knife's asymmetrical grind overall.