From what I have read, that is right. Thankfully the bees don't have a problem with the 1/4 inch. I put it on early to test their ability to move thru the holes. I noticed that even those bees with pollen seemed to get thru they just needed to learn to go at an angle. I even watched some drones move thru.I understand that only 1/4th will stop the pygmies' in Canada.
Today at +4C they were out and flying in the sun looking for water. I filled a tray and they sure spent time filling up.