Well who is defining these religions? From my experience, atheists usually know jack squat about Orthodoxy--at least in America. Maybe the atheists in the Old Country like Russia would know more about Orthodoxy, but since this study was done in Washington or something, I am assuming that it is more closely associated with America. Moving on, most American atheists I have met know nothing about Orthodoxy, however, they do generally know a bit about Protestantism--which is probably what they've been exposed to most. As for non-Christian religions, that might be true. While being honest, most first-worlders seem to know next to nothing about non-Christian religions--at least in my experience. That being said though, it does sometimes seem that most atheists in America do in fact know at least a little bit more about non-Christian religions that American Christians (presumably Protestants) do. Most non-Orthodox American Christians I have met seem to know absolutely nothing about religions other than theirs and have no urge to learn at all, and actually discourage learning about them. Just my experience with this all.