Yeah, I gathered that. Still, it would be nice to see a test like that. I am sure the differences between the encoders would be very small but, if you are encoding your music at the 256kbps bitrate range, then you would care about those slight margins of quality. A test like this wouldn't be needed but it would be nice for curiosity sake. Then again, it really isn't worth running a test just for curiosity.
My canned response:
Why a listening test at high bitrates (192+kbps) wouldn't work:
1) Most samples would have already reached transparency at that bitrate.
And choosing only problem samples would make the test less significant
since you wouldn't be testing a broad range of musical styles.
2) Only a handful of golden ears would be able to reliably ABX the
samples, and even after ABXing they would hardly give scores lower
3) Since all scores would be around 4.5, the error margins would be big
enough to make all codecs tied. To avoid that, you would need to have
hundreds of participants, in an attempt to bring the error margins down.
4) You would have a hard time finding hundreds of golden ears, and even
more, hundreds of golden ears willing to participate, because the test
would be very fatiguing and frustrating, due to the difficulty of ABXing.
5) At the end, even if you managed to bring the error margins down, the
codecs would be ranked so close that you wouldn't be able to produce a
decent conclusion. All codecs would seem (or be) tied to each other.