Now that's interesting! I agree with your findings, there are no noticeable acuity-type differences.
But you do mention "@ 33%" - and this may be the important point. If I view my pic at 33% in C1, I get a good preview, with the same acuity as what you get. But if I go down to "to fit", then the preview is blurry again, even though the difference in size is minimal.
Do you find the same?