I think I found the info you are referring to, "In our factory we edge the blade 60% to the right and 40% to the left, because it is quite difficult to edge fifty-fifty by standard grinding. However it is also possible to edge conversely upon request."
http://tojiro.net/en/guide/part_edge.html
Since it is the edge being discussed, I'm good with that. Easy enough to change, but if the factory has a problem getting and even 50/50 edge, I doubt I could do better. Why would a company say it's "quite difficult" so they proclaim 60/40? Sounds like just a way to justify an uneven bevel, so bias it on purpose one direction.