You can see in the Tundra tooltip that the Action Point cost (for moving up/down a level of terrain) was 2+0. So, he could have gone straight ahead (towards the highlighted tile) for three consecutive tiles, using just 6 APs, and then could have used a dagger attack for 3 APs. If the tile immediately in front hadn’t been occupied by an ally, he could’ve moved one tile at a time, using just 2 APs per tile moved, but the inability to move one tile at a time meant that the pre-selected route had to be used.
