I agree with all your points. But I still think we could've put Jones, Smith, hell even a platoon between Cox and Lyons and gotten 1000 yards out of the B-Back position.
Obviously if you put someone who's slow and small there you won't get 1000 yards. But you don't so that's like a hypothesis contrary to fact. You're going to put your best running back at the B-Back position, and he's going to get his yards, but at the same time I'm just pointing out that even though it is a skill position, players who aren't necessarily as skilled as Anthony Allen are still going over 1000 yards and averaging about 5 yards/carry for other teams that run a similar offense to ours.
I said I liked Anthony Allen at the B-Back, I'm not using his words to second guess him for playing him there. I'm using his words to show his confidence in the B-Back position giving him 1,000 yards. I don't think it's ever not gotten him 1,000 yards...