I think i understand what a Honyaki blade is about - a single piece of forged steel (as opposed to a clad steel blade with softer outer steel and a hard core).
I have read that Honyaki blades have a better edge holding ability than non Honyaki blades of the same steel. Also i have read that they are more prone to chipping than non Honyaki blades.
If the same steel and a corresponding heat treatment would result in the same hardness of a.) the whole Honyaki blade (apart from the upper part of the blade in case of Mizu-Honyaki) and b.) the core (and thus the edge) of a non-Honyaki blade, why should the edges be different in edge holding ability and being prone to chipping?