I wanted to mention the screenshot above because it shows that animations already exist. And we already know that other weapons have Versatile functionality (switching both animations and damage dice depending on usage) so it's not a matter of thay either. It's either that Larian has not yet gotten to make this change, or that they have overlooked it, or possibly that they want spears to have their own animations (which seems unlikely).
The Roman phalanx was the last major use of the tactic.
Norse shieldwall begs to differ.
