I know a good bit more than the average parent about car seats, my family and friends call me a "car seat freak," my children rear faced past one before it was recommended and they sat in 5 pt harnesses until they outgrew the weight and now sit in boosters until a shoulder belt fits them correctly. My four year old is petite and still rear faces in a britax 70. I've posted and been involved on car seat boards for over ten years.
RH told LE he knew the make and model, and weight and height restrictions for Cooper's car seat when being questioned. It would make sense that if he knew of and "was practicing" the one inch rule, that's when he would have mentioned it, and perhaps we will learn he did during the trial. If he was truly a devoted, loving, car seat-researching father, he'd have known not to have the straps on the lowest setting, so those things together are contradictory.
Also, someone stated above that the child's shoulders shouldn't grow above the tallest slot, but for rear facing, the straps need to come from below the shoulder, so it's ok if their shoulders are taller than the tallest slot. The strap has to come out of the slot nearest to but not above the shoulder, when rear facing.
Also, and this is opinion, over the course of having five children and becoming a "car seat freak," I have talked ad nauseam about car seats with my husband. When I heard RH knew make and model of the seat, it struck me as very odd for a dad. I asked my husband if he knew our daughter's car seat brand, my 18 year old also chimed in. I had my husband answer first and he said "Graco," and my daughter answered that she agreed. It's a Britax, and there's a label right above my younger daughter's head every time she gets buckled in.