An occupational hazard of editing, I'm convinced. It's the Someone Else Checked It So I Only Need to Skim Effect. Sort of like everyone at an intersection with four-way stop signs thinking they can cruise through their sign because everyone else is stopping.
Yeah, I heard the "Dyslexics, Untie!" thing a while ago. Still, you don't expect to come across this kind of thing in a document that's been through so many editors you'd think it would have been a fully digested bolus by now.