I do agree the term "polishing" is a poor one and is often used when it is technically inaccurate, nevertheless we are stuck with this term.
My fuel tank has 2 large hatches each 1m wide so access for cleaning is easy. Many boat owners are not so lucky and have no means of cleaning" the tank. "Polishing" is their only option. Cruising sailors report good success with both high and low volume polishing in conjunction with a biocide, in dealing with dirty tanks and/or diesel "bug" problems.
Mechanical cleaning is preferable, particularly when there is an obvious problem, but not all boats can manage this easily, and for many it involves major surgery. So in the real world many rely on "polishing" to treat and/or prevent problems.
My own tanks donít need mechanical cleaning (yet) and I believe my fuel polishing system filtering the equivalent of the tank volume every 5 days or so and removing any water will at least extend the interval of this procedure.
The engine obviously still needs primary filtration and other measures such as filtering the fuel and checking for water before it enters the tank, as well as a good biocide, are essential.
I am finding fellow cruising yachtsmen are experiencing far more problems with dirty fuel and steps taken to ensure clean fuel will help eliminate what is becoming a very common cause of engine failure.