This sounds all very correct, many thanks! I think you must be right in particular about the intuitive sense many buyers have. They must think (having taken the time to notice that one brand's proof is higher than another's, or higher than the same whiskey is offered at in the same store (e.g. VOB often)) that more proof is better, they are getting a higher grade of something.
But do they often know, I wonder, that higher proof means more alcohol?