I don't think it's all that un intuitive, as long as you know that there is an electrostatic effect used for filtering. We all know that it's easier to attract

I don't think it's all that un intuitive, as long as you know that there is an electrostatic effect used for filtering. We all know that it's easier to attract a lighter object with an electrostatically charged ruler, so it's quite easy to imagine that very fine (so, light) particles are easier to to attract than larger heavier ones as well.