Nothing surprising and not the 1st time something like that has been done. And sometimes the suckers... uh... participants... are told that one is a tube amplifier and the other is solid state, or something like that. It reminds of me of something I noticed when taking psychology in college - Almost all psychological/behavior experiments involve deception!
Almost nobody in pro audio does blind listening or blind switching as part of their job and most have never participated in a proper-scientific blind listening test. And IMO, most mixing & mastering engineers over-estimate their hearing ability, just like most audiophiles, until they are humbled by a blind listening test.
I would have asked, "How confident are you?" When you are forced (or encouraged) to make a choice you'll probably make one.
there was much discussion among the membership, describing the audible differences between A and B.
Groupthink tends to make the bias stronger and worse.
An
ABX Test doesn't have red & blue LEDs but it could be valid if "X" has a yellow LED, or something like that because A & B are identified anyway and "X" removes the bias.
P.S.
It's too bad that more of them weren't skeptical of the test and/or skeptical of their own perceptions. WE NEED MORE OF THIS! I don't expect audiophools to ever change but maybe the pros can learn!