Supposedly, the reason we let racks shrink before scoring is 1) so they are all at their minimum size for consistency, and 2) racks can actually be larger in different time periods of the same year, essentially just swollen. Personally, I would tend to agree with the first component, but not necessarily buy the 2nd part unless you're talking about REALLY variant timelines, betting they're largest at freshly sloughed felt time, and smallest/greatest shrink right before shedding.

Frankly, the "minimum size" rule is good in my book, since it ensures that even those old racks that guys had hanging in the den but never had scored could still stand an even chance at the same score they would have gotten when they were first eligible for scoring.