Honyaki and monosteel blades are essentially the same with the exception that one is forged to shape and requires annealing before heat treating and the other is cut from a sheet of steel and requires profilign. After a forged blank is annealed, they are heat treated the same - quenched in water or oil. In US most makers quench carbon steels in medium to fast oil to to minimize warpage, but many still quench in water for more active hamon (W2 and 1095, etc). Rarely blades are coming out of a quenching medium perfectly straight, almost always some straightening required during the process of making a knife.
Hamon on nonyaki is not for decoration but for make the steel to absorb shock better and to make it easier to straighten the edge. Removing scratches (as you know yourself) from hardened monosteel is no fun, and that is where a whole lot of work is. Monosteel blades hardened to 62-63RC, with steels that have some chromium, vanadium and other alloys that are harder than iron, are often much more difficult to finish than a typical honyaki at 64RC or so, let alone san mai with a soft cladding. I can refinish san mai in 30 minutes, while a monosteel blade can take me 2-3 hours or more.
To straighten the edge on a san mai, all you need to do is to bent the spine in the spot where you see warpage on the edge. If you know of an easy way of straightening monosteel blade, I would like to know it, as I haven't found one (easy) yet.
Steels like 52100 is a deep hardening steel because of presence of chromium, so hamon method straightening the edge would not work.
If you use 2 or 3 hrs to polish the blade then something is wrong with your technique.
Most of the polishing as I said is done before heat tread
And yeah exactly stock removal mono steel blades take much less time to make so more profit
To get uniform cooling on the blade, which in turn minimizes distortion (cooling is quite a violent process), the blanks are left at full thickness, including honyaki, which it typically forged thicker.
When I polish a blade, I don't just cover scratches, but completely remove preceding scratches before moving up a grit, that is why it takes me the long it takes.
I have nothing more to add to this argument.
Still 2 or 3 hrs or more sounds like a lot really a lot. I usually polish both Claded knives and Mono Steel knives. I did try to polish both 1095 and 52100 mono steel and time is about the same as Kasumi knives
I will agree that Mono Steel knives Take much more time to Thin, but in makers case it is done on a grinder not on stones !
But polishing or refinishing it Takes about same time for me, and i do not cover up scratches