Chris,
I question the accuracy of the information you were given concerning the following.  While this may have been true in the days of tape and mylar, since it was done by "growing" the entire soldermask layer by photo enlargement, it is not true with todays CAD/CAM tools.  With a gerber file, the soldermask flashes are changed by substitution or changing the definition of the D-Code in use; it does not require enlargement of the entire film.  So, you don't have the non-linear growth you speak of.  Even if the pad geometries are drawn rather than flashed, they can be converted to flashes with todays CAM tools.

<clip>
compensation. They can only compensate soldermasks that are 1/1 to the
lands because any departure from 1/1 results in a non-linear growth from
differing pad geometries since the growth compensation is implemented in
percentage as well as mils, depending on the circumstance. As it was
further explained to me, the degree of compensation varies across a
panel and may be "tweaked" accordingly in the problem regions if and
only if they receive the 1/1 ratio. This actually makes the PCB

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