If you calculate the resolution from that area you will get 13900 from the D800, Of course this means the areas at the blending point and at the floor and ceiling will be interpolated up to 123%.
You got it.
Basically mine is a 2 step interpolation. 1st in ACR, 2nd giving ptgui a crop of about 185 degrees...
PTGUI gives a smart value, trying to even things out and avoid loss of image thoughness.
EFFECTIVE resolution in these case is vapour.
substantially things do not change too much.