The takeaway should be "make sure you can't hit anything". Sitting with your back to the stop often helps you not go flying and hit anything when no proper tie downs are available but it's just a rule of thumb. If you have even just a lap belt your going to be better off facing forward in the event of a crash because of how the human neck works.
http://www.ejectionsite.com/stapp.htm
The takeaway should be "make sure you can't hit anything". Sitting with your back to the stop often helps you not go flying and hit anything when no proper tie downs are available but it's just a rule of thumb. If you have even just a lap belt your going to be better off facing forward in the event of a crash because of how the human neck works.