Yes, to some degree they do, but it is a necessary requirement. The fan has been calibrated to pull in more air, even if it increases friction and reduces airflow. That being said, pleated filters offer more airspace and less restriction — for every inch you get two inches, because a pleated filter has an inch in and an inch out. As they offer better airflow, we recommend installing pleated filters.
Have a look at our range of pleated filters here.