Side to Side Edge Contact

[Bugle999]

Please can someone help with this...
I refer to p.76 Column two bottom paragraph.
Here it refers to the options available to troops in side edge to side edge contact.
quote,
'Battle Groups in side edge to side edge contact are not committed to close combat, and are free to move away. If they do not move away, no combat occurs unless they are eligible to fight as an overlap. IF NOT they can engage in melee as follows.... it then goes onto describe being able to turn 90 degrees to make contact with their front edge (with or without a CMT).
My question is what happens if a BG is in side edge to side edge contact AND also capable of being an overlap - can they still turn 90 degrees (thereby achieving front edge to side edge contact with the enemy) OR does the 'IF NOT' exclude them.
Hopefully this is clear...
MTIA.