That’s an excellent question. The more a blade is flat and parallel for heat treat, the better chance it has of staying flat when it is quenched between the thick aluminum plates. Some makers just profile and drill holes before heat treat – and they grind the bevels almost entirely hard.
My preferred choice is to profile – drill holes – and then grind the beginning of a bevel – maybe only ¼” high and leaving lots (maybe about .030 on the edge). This still leaves a mostly flat and parallel blade between the quench plates, but takes away a little of that 90 degree angle that just shears the grit right off your sanding belts.
Now, the above presumes stainless blades which get plate quenched. Oil quench blades are a different animal – the thicker the better. There is no plate to keep them flat and warping can be a pain to correct. (We don’t do it).
Hope that helps some.