How would you unethically test ancient combat tactics? Unless you mean have people try it until it seems to work, in which case, I'm sure you would find many willing LARPers
I think the issue is that LARPing battle is a poor substitute for what the body can take and how people respond to real pain and damage. We might be getting to the point that we can get somewhat of a foot take on the damage with VR eventually.
You also have to grow up in a society that is completely alien to ours, your entire outlook on life, how long you might live, and how willing you are to give up your life is different.
Imagine living in a world where how tough you are, how well you can fight determines everything about your status in the world.
I've been playing Blade and Sorcery in VR for a week or so. It's scary at first, but after a while I don't mind getting hit and play in a way that I would never do with my own body at risk. In the real world I'd get somewhere up high with a bow, but I run around like Conan the Barbarian in the game.
The conjecture is that people will not willingly throw themselves on a line of spears and so the phalanxes would stop short of actually hitting each other. I don't think larpers would be able to test that well. I'm not sure how you would test that unethically
I feel like a great deal of melee warfare involved group A smashing itself upon group B. Phalanxes, as I understand it, were effective because they were particularly good at this part. So given that we already had lots of other varieties of troops throwing themselves at the spears, why do we doubt that other phalanxes would specifically be unwilling to do the same?
The idea is that a phalanx trained under the assumption that their formation was nearly invincible as long as they were experienced enough and worked together well. Both the members of the phalanxes and the generals would be hesitant to risk that by sending them against another phalanx where they lose all their inherent advantage and would need to fight in a different way.