TB: You are correct in your assumption. However, I have a 4" 200 mesh in-line filter before the pump (inspected/cleaned every 2-3 weeks) and still wound up with clogged mist heads. My heads have tiny, cleanable, screens, which had actually clogged. (edit: I run RO water through the entire system, then break everything down, including mist heads, and clean them between grows.)
I am hoping the easy access post pump filter will eliminate having to take the heads out and clean them during grows. Not a big deal, but if your heads are remotely clogged, the amount and quality of atomized mist will suffer. What I don't know, although r0m30 kindly posted the info, is what that means in the real world of pressure to the heads.
I ordered 2 from Fresh Water but they were not in stock. Keep you posted.
hth