About how old are the Japanese razors?
The ones I have 50's and later. I think it had to do with the honing style of the Japanese barbers. No proof, just a suspicion.
On the other hand I have gotten modern custom razors that were under honed on the toe. You could see the bevel setter scratches but it didn't move beyond that. Needless to say they had to be rezoned because I really use the toe, more than the heel.