I have not gone the gauge pin route, but with an outside micrometer and neck thickness micrometer, both reading to .0001, I don't really feel the need. In any case, long ago, I noticed the comparison between the force it took to seat bullets in cases that had just been sized, and those that had been sized a couple of weeks earlier. I thought that it might be something about the grain boundaries of the metal being disturbed and then resetting over time, the new configuration becoming normal. This would not necessarily show up as a dimensional change.
A while back, a friend who was working to wring the most accuracy out of .17 and .20 Ackley Hornets found that getting the neck tension right and very uniform is very important to the accuracy of his ammunition. He worked with expander mandrels polished to very slight variations to find the best tension. A friend of his got into machine annealing as well, for the same calibers. The results were unambiguous. Not only was having the right neck tension important, but uniformity was as well.
I think that as sectional densities increase with caliber and bullet weight, these factors may become less of an issue at more normal ranges, but for the short bullets, in the smallest calibers, bullet pull is a higher percentage of the the resistance that must be overcome and start the bullet into the rifling.