[Greg Wormald]

I'm going to assume that like most other training, the improvements in
performance can be incredibly specific.

If this is true, then the differences they may have heard in their own
equipment comparisons would not necessarily transfer to the ability to
hear differences due to compression artifacts.

All the same, I do find it surprising that they did so poorly.

Maybe they were so trained to listen to equipment, that they don't
bother listening to the music. :-)

I'm sure there are other explanations/options/interpretations.

Greg