Yep. I've been doing histograms like that for awhile just to spot how many tool sets were involved. The width gives you sorting information. Here's one for some Winchester brass that I actually did using some new bulk purchase Winchester cases, but later drew from that data.
Here's a photo of a sort of some LC .30-06 brass by neck wall runout. The left side is zero (actually <0.0005" TIR) then in 0.001" steps to the right:
Regarding water capacity, the main purpose is to allow for the individual chamber's size, which is mainly useful for getting QuickLOAD optimized for a particular rifle. Once you've found your load workup range, though, as you say, just going by case weight difference is really all you need or, unless you're nuts, want to take the time to do.
I find water capacity prediction from weight is usually within 20%, with the error due mainly to differences in head diameters and differences in the angle off the extractor groove going forward. So when I suggest Mr. Pond's Norma cases will need half a grain (actually 0.48 grains) more powder to match the pressure of loads developed in Lapua brass, that may actually be off by about ±0.08 grains. Close enough.