I don't think you can safely make the assumption that a hit to the body is the most likely outcome, considering that the game models the hitbox as a cylinder; 100% accuracy is hitting within the target's tile/cylinder. A Gaussian distribution would be great if you knew exactly where you hit on the target, as a given projectile and velocity does have an expected amount of tissue damage it will inflict. But then we have to make a distinction of what you hit, as you'd expect different amounts of damage for multiple body parts. To account for that, we could make a damage distribution for each body part. The result is that any given bullet falling within the cylinder of the hitbox will fall on one of these distributions - if for simplicity's sake we want to make only one roll for damage, the amount done will have a probability distribution that looks like a weighted sum over many Gaussian distributions, each with a different mean and standard deviation. The final distribution is flatter than a Gaussian, and while it may be biased toward the body shot result, the width of the distribution would look much more like the flat case.
The point is, short of coding in better hit detection - body vs limbs vs head, influenced by firing accuracy - or adding in some method of critical hit/miss, a single Gaussian alone is a gross oversimplification based on a very particular set of assumptions. Flat is a great simplification too, but Gaussian is too elegant, clean, and symmetric for something as messy as RL combat.
Now if you average over many flat damage rolls, that does start to look more Gaussian - this was more the route gone by the reboots; you never just fire a single shot from that assault rifle, and you can probably assume your sniper is hitting center of mass. Critical hits and kill shots are even animated as hitting the head.
Edit: @Surrealistik The likely reason you're getting so much flak over the suggesting switching the mod to Gaussian damage model is that it is balanced for the flat distribution, and making the switch means each weapon has to be looked at compared to armor values, and one or both would have to be changed, for some ~300 weapons/ammunition types and ~50+ armors. This is a massive amount of work for Dioxine, who'd probably rather spend the time implementing new features. The other option would be a change to the executable such that no rebalance is necessary - adding critical hits/misses, some manner of firing accuracy influencing where you hit on target, or implementing a Gaussian distribution with added probability in the tails to account for headshots/deflections, which would be more work for Meridian, who is busy with coding in other new features. If you really want Gaussian distributions to be the norm, I'd suggest trying to mod in the balance yourself, or make a fork of OXCE+ to test out how to make it a better model.