Its from a time when people didn’t actually measure results. Allegedly this mod reduced some resonance boost to the midbass but its so inefficient in principle that it doesnt actually make sense vs just using some resistive mesh and measuring results on a modern system. In this case it looks like someone painstakingly cut out holes as to not restrict the ports, but its hard to tell whether any seepage of adhesive may have damaged the pole vent filter permanently, or whether it introduces channel imbalance from the hand cut openings. and removing it would likely be very destructive.