These are good points. However, I believe that the outcome of these tests negate the friction argument because they were presumably tested in the exact same manner. I am referring to SRL's test BTW. From his tests, the Z2 and
SG didn't remove any of the marker. Granted, there could be carrier solvents in the
NXT that just happen to remove sharpie, but don't necessarily mean it has cleaners, but it also indicates that there is the possibility which there are cleaning agents in it. This has been since confirmed by the manufacturer, thus perhaps this test was more valid than you seem to believe from your post.