@lewm I have done that test. I cleaned most of my collection with a VPI 16.5. Then I bought a German Elmasonic 80KHz US cleaner and built an RCM around it. Then I cleaned my entire collection on the US setup.
Using the few uncleaned, but carefully handled since new, records to calibrate the test, I noted how much gunk was present after US cleaning 50 records. Visual observation only, of residue and colour of fluid. No accurate measurement, no photos, sorry.
Then I cleaned 50 more records, in new fluid, which had previously been cleaned on the VPI. About the same amount of amount of residue as before, colour less changed. A second US cleaning in clean fluid produced essentially no more gunk, although in problem cases multiple US cleaning improved sonics..
Cleaning with US improved sonics over VPI. The improvement was about equivalent to upgrading a major component. An added benefit is stylus wear.
I had a photomicrograph taken of a Koetsu after nearly 1000 hours of play, and it showed, according to the dealer, "minimal wear", which is what I thought. He went on to note that I should not even consider rebuilding it, "unless I had a whole lot more money than he thought I did." So it looks like my cartridges are wearing very slowly, and the US cleaning is not only paying for itself, but paying dividends.
I am careful to do heroic rinsing, 2 rinses in pure running water, followed by a distilled water bath and then distilled water spritz. I also use a lab grade detergent from Fisher which is especially formulated for plastics. 80KHz. New sleeves. With other regimes, such as diluted alcohol (Danger !), I have no idea, so YMMV.