There will be flanking of a sorts in this game without unit facing taken into account. Just play PG and you'll see.
yeah, this. With only 1 UPT, the only way you can take advantage of superior numbers is to flank the enemy. That's pretty much the reason it's used in real life too, to concentrate greater numbers against the enemy. You can also use it to sneak past frontline units and attack support units like artillery. But adding this "facing" system is just hugely artificial and annoying. Are the soldiers too stupid to turn around when an enemy unit comes up behind them?