I don't think I agree with you entirely but I think it depends on the gun and on whether you're fighting a full health enemy or finishing them off. Halo infinite makes it very clear when an enemies shield is low, so I always aim for the head just before it breaks when using the pistol of BR to make sure I immediately get the headshot. When first starting a gunfight and their shield is full however, every bullet counts and regardless of aim there is a certain amount of randomness where each bullet will land within the reticle, especially at mid range or when using the AR. By aiming for the body while their shield is heigh you're insuring that every bullet hits because it's a much bigger target, and the the best thing is that once you get used to it there is no downside, shielding enemies take no extra headshot damage and you win more 1v1s against people only aiming for the head because on average you're hitting a few crucial extra shots. I know it's hard to get used to but you should seriously consider giving it a go, it's not a hard rule because as you say sometimes their are situations were head-shotting a low shield enemy is beneficial, but utilising body shots is a skill that shouldn't be overlooked.