Over multiple rounds and different positions I didn't get a flank bonus. I am unclear if it's that terrain area or the Harrapans runner that can never be flanked.

auto-save 1199.ctr

I realized now that moved out of combat with the initial unit in the original turn load and fought a second unit. Maybe it might just be that specific battle. Because I had moved out of zone of control with another unit and then into combat with another?