At the end of the day, a bass is made up of a set of component parts that each add to the “sound”.
In the main, these components are pretty much alike from one bass to another - strings, bridge, tuners, wood, pickups and how they are made/wound.
We formulate and process information in our brain from a mixture of sensory sources - I’m not surprised there was little discernible difference in an audio only test as nobody had the visual cues that our brain often uses to interpret sound..