Tim:
Scott-Although not the furthest point away 9 green does not come back to the clubhouse. Isn`t that what denotes an out and back?
To me an out and back routing is easy to identify: it goes out, then it comes back.
It might kink a bit here and there (R. Cinque Ports, The Old Course), but by and large that is an "out and back" routing.
National is out and back, Fishers Island I would say while "non-returning" and "an 18-hole loop" is not. Even The Valley Club -- which has loops from 4-7 and then from 8-10 that begin and end more or less where the 3rd green and 11th tee are -- is often called "out and back" and I don't believe it is. MPCC Dunes is much the same.
As with the term "links", I think "out and back" has been hijacked somewhat in the 20th and 21st centuries to describe courses that are not out and back routings.
If you look at the likes of Burnham & Berrow, National, Brora -- that is out and back.
Pine Valley as the example here has a loop from 1-4, 7-8 play in complete opposite directions, 9-11 is a little loop, 15-16 play in complete opposite directions... in my book it's about as far from an out and back as you can get.