Just to correct some previous information: the trim-to length is not the minimum. If you look through the SAAMI drawings (
links are here), you'll discover that most rifle rounds have plus 0.000", minus 0.020" case length tolerance. The trim-to length is simply in the middle of that, largely because the cutters used by the case manufacturers aren't as precise as a lot of hand loading trimmers are, and new cases can sometimes vary a number of thousandths, case to case.
Maximum length is a critical number. Too much length can jam the throat of a chamber and raise pressures rather substantially.
Minimum length is a non-critical number and is really only specified so bullets that will be crimped into their cannelures don't get seated too deeply into the case. If you ignore it, and trim more off, as some .308 match shooters used to do so they didn't have to trim again before they tossed the brass, there's no inherent safety issue. But in that instance they were loading match bullets to magazine length COL with no crimp, so as long as they kept their COL the same, there would be no substantial effect on pressure from crowding the powder charge. A benchrest or varmint shooter would want to keep neck tension more consistent than that, and I'm not recommending the method because of that; just pointing out could be done without creating a safety issue.