Read through all of this only now; if I did not miss,
I would imagine that some sticky dirt would take time to loosen up, seeing as to the amount of time it might have taken to attach itself. How long do folks take over cleaning - leaving it in the liquid of choice for days, perhaps? Even ultrasonics do not always work instantaneous (from my experience in cleaning other stuff at work).
My oldest (first) record is Student Prince (Mario Lanza) bought new about 1955. Some scratching seeing as how it was initially played with a crystal cartridge, stylus pressure not much less than 3 gm, and quite a few other cartridges since .... But vinyl will of course wear, especially if more than 30 years old. As said not all noise is dirt. Some of my records stayed much more noise-free than others over the years, but comparison will be useless, not knowing how many playings under what circumstances, etc.
Off-topic, I have some problem with stilii riding on various places in the groove. There is really only one optimum position, especially with stereo. Noise-wise one might have an improvement, but there will be some deterioraton in fidelity - tracking error, tracing error, bounce, bias force, exact position of stylus shank in cartridge ...
