When the capacitor was replaced, it was more a matter of drift than noise, at least that's how I understood the posts, and that's how an improvement was achieved.
So if he's already replacing electrolytic capacitors, then he might as well replace the electrolytic capacitors of the actual supply.
If I remember correctly, all supplies in the system are linear and not switched, so the ESR question hardly arises in this respect.
However, I agree with you about other capacitors in other circuits of the system.