I do dispute that you actually gain anything beneficial by downscaling a high megapixel image to a smaller size, in a real-world context
Actually, we agree here. When you downsample, you trade resolution for lower noise. You're not creating a higher quality image. Depending on the situation, it might or might not be a tradeoff you'd want to make.
Agreed. From the standpoint of normalizing noise to compare how noisy one sensor is vs. another (which is what I gather the DXO Print DR statistic is all about based on the arguments from you an LTRLI), then sure, you should be normalizing image size.
I'm glad we agree with this, because this is basically my whole point -- if
you're comparing sensors, then you really should use the print measurement. If you're using the measurement for anything else, then the "screen" DR is as good (or better)
I can understand that from the perspective of having already picked the camera and wanting to measure its DR for purposes other than comparisons, parsimony rules, so I understand your preference for the per pixel score in this context.
But DxO are really in the business of publishing benchmarks that will be used for comparison purposes, which explains their emphasis.