Agreed - there's no reason to risk it, and really nothing to be gained. I was only curious because I just started reloading .380 and I noticed that so many of the recipes were only a single value, rather than a range of charge weights.
Read the whole manual. As noted, Lee just reproduces info that was published by other sources that actually did the testing. Companies like Alliant only publish the max but tell you in the text of the manual to download 10% and work up. This is listed on page 8 of their current manual. http://outdoorwriters.atk.com/resour...derCatalog.pdf