Absence of Proof is not Proof of Absence. Nor is it proof of existence.
Collecting evidence for either side in this case amounts to the same thing... listening to the box compared to other boxes, over a very large sample of listeners...

Bottom line, I am not sure why we are trying to "prove" anything. Its not like the Outlaws are showing up at people's houses and forcing them to buy a 990 at gunpoint. I am sure the Outlaws would love to sell a unit to everyone.. they took their best guess at what people would buy at price point X, with feature list Y, with costs that allow X > Y to a point where they can pay people's salaries, their suppliers, the landlord and hopefully have a little left over for investors. Given the multitude of variables and real world constraints I am not surprised that everyone does not find the 990 perfect, or even desirable.