I’ve noticed that if you have in your hands something like the hammer or a grenade and you switch to another soldier in the squad, the AI controling your previous soldier will keep the hammer/grenade/whatever in their hands.
It also happens if you order an engineer to build something. Once finished, they will keep the hammer in their hands.
AI is (usually) not really good at killing so if they keep in hand something they can’t use, it’s not helpfull at all.
Therefore once the player switch soldier in the squad, the AI should directly take the primary weapon in their hands. (or take secondary weapon / pistol if out of ammo)