Once the subject came up, I decided to go to that so-so source of all information, Wikipedia. After learning that the relevant definition of "production art" is the work of a "production artist" (what a surprise), I saw this in the definition:
"Per Comic Book historian Mark Evanier, in that industry the position generally has involved into "lettering corrections, art touch-ups, laying out advertising and other editorial material and generally doing whatever in the office required the services of someone who could draw a little." I don't consider clean-up work to be artwork.
Now about those color guides, what do they do that really is artistry? Tell the printer exactly which Pantone number to use for publication? Hand coloring won't necessarily match the final output: it's a guide. So calling it "production art" is essentially saying it's not art. It would be like someone was claiming West Virginia is Virginia because they both have Virginia in the name. For that, Heritage is on target.
"Unoriginal art" is what I would consider re-creation art or copying. So the phrase "original art" does have some meaning.
As far as collecting art by character...it keeps the collection focused. It also lets me appreciate different styles because the variables of a different character or scene are removed. I do buy other things on occasion, but I like my focus, thank you, and it is not a "production."
As far as my legal work goes, a lot of it involves contracts. You bet a comma can makes a difference, but the key remains context. The context of the phrase in what I had written was clear. If not then, certainly now.