I still haven't got a clue what is being discussed. Is the hollow, or concave, or swayback, or poor posture...

1) on the top of the spine (meaning directly opposite the edge and when placed down on the flat surface the blade is perpendicular to the surface and the edge is pointing away from the flat surface).

or

2) on both sides of the spine on the areas where hone wear occurs (meaning the blade is parallel to the flat surface).

If #1, then that's just a typical spine for a smiling blade.
If #2, then that can be uneven hone wear.