You may have had moire on some test images, but one thing I've noticed is what appears as moire may not really be moire. In several cases I have seen moire on a screen but found that when I zoomed in for a closer look, there was no moire. The same has been true in looking at JPEG's and in one occasion looking at prints that had moire even though the NEF did not have moire. The reason is the D800/E can reveal resizing artifacts both when an image is resized as well as when it is simply viewed as less than native size on a computer monitor.
It's normal for moire to go away with a teleconverter as you get a little softening. You would also be at a different distance which is one of the ways you eliminate moire.
Overall, your findings are somewhat different from my experience in the field. Upscaling can lose some detail, and may require an extra step of sharpening or contrast to recover that detail. DxOMark shows about a stop or more of difference in visible noise and other factors due to image size.
Your tests do not show any impact of diffraction. Most other tests are showing a small amount of diffraction as aperture goes above f/8. Diffraction may not be as great as upsizing difference, but it is a factor at f/14 and f/16.
Now I do find your comments interesting. I think it's important to understand your camera and lens combinations and how they perform. I wonder if there is a small focus error that could be resolved with AF Tuning - or left alone if it produces better results for your photography.