Well you can say it is just your opinion Chris, but the physics that govern the properties of the steel hold the exact same opinion, so you are in pretty good company. If one defines the "strength" of a material its resistance to deformation, ductility is virtually the opposite property. Avoiding the hardening of around 2/3 of the blade is replacing all that strength with ductility. Materials with much lower impact toughness, like very simple iron-carbon alloys (bloomery material, tamahagane, etc...) may avoid breaking with such a treatment, but would also bend rather easily. Modern alloys have a much higher toughness and are only robbed of overall strength by partial hardening.
Also, for what it is worth, not all acids are the same. I have an entire cabinet full of different acids, and other reagents, that need to be used to bring out any number of different microstructures in steel for metallography. Straight HCL or muriatic, is not the same as FeCl. FeCl is HCL that has been supersaturated with an iron solution, that is why you need to dilute it to get it to cut, it cannot hold any more iron at full strength. This chemistry causes FeCl to not only remove material but also deposit a dark oxide on the surface of the attacked metal. HCL, or muriatic, is more aggressive and so it only dissolves the metal while leaving it a dull gray on grey; it also will pit if not carefully monitored. But one can use HCL to get a topography and then color with other etchants, it is just easier to do both with FeCl. I personally despise the look of an FeCl etched hamon, and prefer to use other acids that will turn it bright and glowing with highlighted activity, to show off the actual heat treating effects, rather than just make a mottled grey blade.
