You are right about the expression " expectation bias"... It is used In a scientific test conditions environment...
But in ordinary life our "expectation biases" pertaining to our own gear can be dependant and vary in function of our hearing history and culture... The japanese audiophile dont favor exactly the same speakers design colors than some other cultures.
Then before conducting a scientific test we must sample the subjects used to understand also who they are ...
Or we can use very varied large samples in some studies etc ...
Expectation bias generally relates to experimental design flaws, not (in this example) to subjects’ perceptions in a study. If expectation bias were involved in that study, it would likely be a fundamental issue rendering the investigators’ discussion misleading, as they’d be premised on spurious results.
This is an example of why it can be hard to discuss such topics in audiophilia - there’s a “minimum height requirement” in background knowledge for stuff like this to make sense among back-n-forth discussion (i.e. > 1 person). 😉 I know that looks reeediculously pretentious in print (Eew!) - I’m sorry, and I mean no offense. It just is what it is.