They left shaking their heads because when they compare the same preamps one at a time they "think" they hear big differences.
They do hear big differences at home. No doubt about it.
Long term listening does reveal bigger differences than short term listening of unfamiliar complex systems, rooms, etc.
Especially unstressed at home ---long term differences being notable -- with the entire home package being a familiar.
Anything else being paraded about....is well, horsepuckey of the most damaging kind.
Read up on listening tests and the human ear. It’s not a machine, it’s biological, and is individual and has learning curves, and these aspects take time. the ear is a living moving changing variable. and different in every single person. Seven billion different sets of hearing.
It even possesses intelligence and capacities levels like minds and IQ. Yet most people don’t mention these entirely obvious realities. Like your eyes, and mind, they come with a almost totally blank page, and you build it out from some very basic starter forms.. You learn your way to hearing, with your individual package that has as much variation in individuals as does IQ.
Bamboozling them with a test that no one can pass, without adequate amount of time spent in front of it, does not substitute for hearing knowledge and skill.