Othismos: Classical vs Crowd Theory Othismos

[Giannis K. Hoplite]

I'm not trying to find a direct analogy,but isn't it interesting that ina pushing match,the teams mainly push square on? Their position changes a bit 3/4 but never do they go vertical. I don't see why this ought to change with a shield? Or perhaps i need to see it happening to understand why it wouldn't be the same.