When units call out directions the direction is based on world north instead of group heading. For example, if the group has been running south for an hour, then an enemy is spotted north, they'll say "Front" instead of "Back".
Same goes for ordering moves. If you've been heading south for an hour, and then order them to move left (west), he'll say "Move right".
In fact, this applies to anything that has a direction. Whether spotting targets, ordering moves, or ordering targets, they'll say "Front" if the target is north, "Left" if they're west, etc. instead of relative to the group heading.
This makes it extremely confusing with AI, or without mics in multiplayer.