That's another oddity here. I swear that I've heard many times that it's a penalty. Even if there's no contact, if you block the receiver's vision without looking at the ball, it's a penalty. I've heard that a million times, and over 500,000 of those related to William Bartee. In fact, I think it's even called the William Bartee Rule.
That's a great example. And that was even pre-Manning rules. They've always nailed DBs for it.