Slitherine

Here's a situation that occurred in a game recently.
I understand that when a unit breaks and has enemy BGs in contact to the front and a flank at 90°, the rout direction is the bisected angle of 45°.
So, when a unit breaks and has enemy BGs in contact to front and rear that'll be 180° so the bisected angle is 90°and so the rout direction is either left or right if the routing unit has room to turn.
For example, a 2x2 BG of cavalry or light horse that breaks and has enemy to front and rear can turn to left or right but not remain in 2 columns because there won't be the width (80mm into 60mm space) so can drop into single column (40mm), not shifting more than one base width and routs from that position assuming there are no enemy units in it's path.
Is this correct?
Thanks in advance for any replies.

Yes that is correct. the routing BG will turn 90, contracting if needed and then do its rout move. Of course, you then get the issue that the routing battle group can turn in one of two directions. If it can complete it's rout move in both directions (i.e. by turning left or right as it were) it is up to the player owning the routing BG which way it goes.