Sitting in the back rule. is not in print anywhere, as far as I can recall. It's one of those rules that came from an Elders school that the Elders had to pencil into the Elder's manual. It came before my time as an Elder. An older Elder showed his book where he had written in his older book. He stated that it was information in the 70's. That book, he showed me, has been revised three times since then. The rule has lasted until now.
Sitting in the back row for DF'd ones has been a practice in our city for decades.