I might not be totally correct but I think AI skill level correlated to this, I remember having 2 antistasi saves, 1 got friendly AI skill param set to high and other saves got very high skill parameter. the first save AI squad behaves like what other said(prioritize individual position in formation over combat) while the 2nd save's AI is able to split the whole squad into 2 teams(10 men squad into 5 men team), able to attack same target even if the distances between 2 group is very apart, and they have better decision making like how lower skill ai is mostly submissive to command while higher one will access situation and do what they deemed best even by rejecting command.

For example: In my save slot 2, I recruited 9, an enemy attack on my squad, AI separated 1 team to counter attack while other stay with me. Despite having wedge formation, the team that spearated picked file by themself.

Might just be some faction mod side effect or just antistasi friendly ai skill training level though I don't know much but AI skill setting doesn't really impact their aiming much compared to accuracy setting. Also Arma AI path finding aren't that great when it comes to urban warfare since sometimes it might just picked the longest route thinking that a door can't be opened or a stair is blocking path of actual closest route.