rudder is linked to the aileron
As far as I know none of the aircraft I have flown have this feature. (You can turn it on in Flight Sim though!)
According to the book it's sound aerodynamics. The rudder is only needed when banking not when banked (if you know what I mean). It makes sense if you think about steep turns - in fact the author says it might be a good idea to teach steep turns before shallow ones! It also goes on to say that turn coordination is primarily with aerelon and elevator back pressure.