I thought about it for a bit and I guess the answer is pretty not-exciting physics-wise.
The march skill is a fixed length/width 'box' that approximates a vector field. When you see:
![enter image description here][1]
The reasoning is going diagonal through a box maximizes the distance traveled within the box.
![enter image description here][2]
How anti-climatic. [1]: https://i.sstatic.net/0RpEH.jpg [2]: https://i.sstatic.net/qANgt.png