To a certain degree this makes sense. St. Thomas teaches that we can know of the existence of God simply by natural reason. Given that God is knowable with the human intellect unaided by Grace, it stands to reason that the anti-faith of an atheist would mean being able to explain away the positions held by theists, which means knowing about what various religions say about themselves.
Then again, this study is really pointless. The larger trend seems to be that the prevailing religion these days is non-religion, not anti-religion: more people don't know and don't care about religion to even bother with the effort of being atheist. And it's a lot harder to convince someone who doesn't care about the Truth to accept it that it is to convert one's misconception of it.