If one is testing to determine if any differences can be heard, then any unnecessary alterations should avoided. Simple idea, one can argue that the alterations interfered with the tests, you can be certain that those who worship hirez will use that as an argument.
From my observations here and elsewhere high rez proponents do not need rational criticisms they have a vast arsenal of attacks such as (all found , none made up)
1) You must be deaf if you cannot hear a difference
2) Your kit is not good enough if you cannot hear a difference
3) I don't need to submit to a blind test, I know I can hear a difference
4) The source material was not good enough to be able to hear a difference (sometimes this argument may be justified see Meyer and Moran)
5) You are not listening seriously enough to hear a difference
6) 16 bits cannot properly express any real world analog sound
7) Just because scientifically we can't hear something doesn't necessarily mean we don't perceive it
8) Music is not sine waves
9) High res provides more nuances, transparency ambience and realism
10) There is something missing from red book
11) higher frequency content isn't to capture nominal or "carrier" frequencies above 24khz, but to capture the small fluctuations on frequencies in the audible range
12) 16 bit 44.1-khz sampling "absolutely demolishes any part of the signal above 10k"
13) DSD introduces a sound signature that PCM does not inherently have, and this sound signature does not lend itself to digital down conversion to 44.1khz/16bit PCM; but it somehow is able to come through if DSD is converted to analog first.
14) I can hear a difference
15) There is obviously a difference
16) I can easily tell the difference between CD version and highres version of the same remaster. It is simply sounds more sophisticated and less harsh.
17) I can hear a difference
18) there exist audible signals that cannot be encoded transparently by a standard CD\
19) I can hear a difference