Good article. It's what someone has been saying here for some years, cellulose fibers themselves can absorb particles, very fine ones, while slick synthetics can't. That's why if the sentence is read in context, cellulose fibers can extract more dirt from the oil while the surrounding pores remain open than synthetic fibers. Synthetic fibers are something like fishing line, they don't absorb and are smooth and slippery so dirt doesn't stick. The filtering is done solely by the holes made from crisscrossing of the fibers. Synthetic filters often have listed higher capacity for other reasons like they have more depth I believe. But down on the micro scale a cellulose fiber catches more just because of what it is.