there are no audible distortions in a pot....you say you hear them and offer no measurment ideaology in return, thats not getting us along in this thread with any meaningful info IMO.
My concept is that which is expressed over and over again in the literature, which is that unprotected metal to metal, or similar, contacts are intriniscally subject to corrosion or buildup of contaminants, irrespective of the quality and type of metal used. I have already mentioned the incident of an air force jet crashing, which the enquiry blamed on the gold to gold contacts in a wiring harness connector corroding. Solder provides a very effective air tight sealant for connections, I don't think you have to be fussier than that.
It's also an accepted behaviour of contaminated metal joins to exhibit diodic behaviour, that is, there is some significant level of rectification taking place with AC signals. The maker of the Lightspeed Attentuator was able to observe the non-linear behaviour of very high quality pots on a high speed storage CRO, which is where the finger on the pot reference comes from.
How the Benchmark, say, could be measured is to focus on high audio frequency behaviour, IMD with signals at very low levels, say 40, 50, 60dB down, and there has to be a time dimension to it: do the test immediately after moving the pot wiper, then 5 minutes later, half an hour later, that type of thing ...
In the end the only thing that matters is that there is some behaviour or phenomenon occurring which is repeatable: a precise explanation of why it happens is not essential for accepting that it does occur, and that therefore some means should be used for dealing with it ...
Frank