You're correct about the original application of gauze filters. Another common misconception is they improve air flow to the combustion chamber dramatically. They are less restrictive but the air flow into the combustion chamber is determined by the exhaust system, not intake. Reducing the dP of the intake filter slightly alters the air charge since it takes less suction to fill the chamber, but the suction is determined by the piston stroke and exhaust system eduction effect at the collector. As exhaust gas goes down the pipe it gets to the collector which is a volume expansion in the system. The rapidly increasing volume causes the gasses to accelerate reducing the back-pressure to the combustion chamber. At that point the exhaust valve is fully open and the intake valve begins to open. As the intake opens the rapidly lowering pressure in the collector creates a vacuum effect since it's lower than atmospheric pressure with rapidly expanding exhaust gas, drawing fresh air in as the piston begins its downward intake stroke. The intent of this type engineering is to remove as much spent fuel gasses as possible and add fresh air for the next combustion stroke. If there were no eduction in the collector, then spent gasses would remain in the combustion chamber when the intake valve opens and chamber pressure reaches 14.7 psia (atmospheric pressure) from exhaust back pressure. Any gain from lower dP filters is really negligible to the overall system efficiency.
Another key aspect of filtration is that the more the filter loads the more efficient at removing particulate it becomes. As material is deposited on the filter media it creates a mat that filters particulate before it gets to the media to be trapped. The only drawback is that when the filter is at its maximum efficiency the airflow becomes restricted. Restrict it enough and the filter collapses under the stress of piston suction negative pressure, allowing unfiltered air into the system. So, when it comes to your air filter, whether paper or cotton gauze, some loading is better than no loading, i.e. it works better at removing the bad stuff when it's a bit dirty than absolutely clean (or new).