I noticed that if you select a group of infantry and send them to form a line at a position off to the right or left but ending up facing to where they came from, ie they would have to rotate once they arrive at the position, they will not rotate.
Vehicles will rotate but infantry won't. So it seems like a bug with the infantry formation/facing mechanics.
This was tested with U.S. infantry
Edit: U.S. Helicopters and Osprey displaying same facing mechanic error. They will not take on the ordered facing once arriving to destination.