Seems to be too many variables, and it would require much more testing to remove them. Quality and consistency of the abrasive, the substrate, the skill of the user, force/speed/consistency of stroke against the wheel, the condition of the steel microstructure, etc.

I wonder how hot the edge got. 90 RPM is pretty slow, but Roman Landes recently gave a demo at Ashokan where he shows that the edge can reach a thousand degrees while sharpening. Diamond (carbon) will break down when working steel (iron + carbon) on some power equipment, I wonder if that is also a potential factor fpr the test.