How high the outer layers grind up the side of the blade depends on a number of factors:
Thickness of the outer layers vs. the billet/final forged stock thickness
Height of the grinds vs width of the billet/final forged stock thickness
Radius of the hollow grind
That being said, and all things being equall, I suspect the differences will be very minimal between a flat and hollow of the same height, unless the hollows are very deep and the outer layers very thin. Even then though, I don't know that it'd make much difference.