Since you are a scientist you should presumably accept that human bias is likely to be present in all those uncontrolled listening reports that you refer to. Or was there a controlled study of this that I missed?
No-one is immune from expectation and confirmation bias, even if they’re fully aware that these biases exist. Occam’s Razor says this is the most likely explanation for what people are hearing, given there is – at least currently – no evidence for any objective difference in the DAC output depending on whether a generic switch or a so-called audiophile switch is used.
The scientific process would involve presenting an alternative hypothesis as to why these differences might be observed and then developing tests to disprove or add weight to that hypothesis. Simply saying “I [and others] hear it so it must be real” is not in itself science, and does not mean that current science is inadequate to explain what’s going on. It is an informal observation, nothing more or less.
I’m not arguing about what you hear or trying to tell you you’re wrong, but your subjective experience with or without an audiophile switch is not really of any significance either to me or to the science of the matter unless it’s based on a properly controlled test.