Which would be true if damage to, say (assuming all fired from the same position), the lung had the same net effect as damage to the pocket of the shoulder, or the side of the ribs, or the thigh. There's good reason the trauma plate isn't huge on class two-plus armor; it's there to protect direct shots from front aspect to the heart, aorta, and vena cava.
The difference between a lethal thigh hit and merely temporary disability thigh hit is measured in single digit millimetre differences in location. Likewise the pocket of the shoulder - if the stretch cavitation doesn't rip open the major arteries and veins, those locations are impairing, but not lethal, and full function (≠ full healing, mind) can be, depending upon exact path, a few days to a couple months. Open the major veins or arteries, either by stretch cavitation exceeding elastic rebound of the vessel, or by penetrator actually directly slicing, and life expectancy is minutes, with potentially little to no disability prior to vascular collapse from lack of blood volume. Which can be seconds to double digit minutes, depending upon which vessel and where along it. At the same time, said vascular hit can result in major loss of long-term disability by tissue damage from oxygen deprivation and/or inability to restore supply before necrosis and/or infection.
It's also not unlike how a few inches difference in a fireplace log to the underbody of a truck... if it pops the air brake line (pulling it from the connector, cracking the connector, or snapping the hose, the rig's going to stop, and possibly damage the transmission. If it cracks the transmission case, it may do very little damage. If it hits the frame, it's unlikely to matter as a single impact. If it hits the fuel tank, it's a slow loss of function, but one that can be easily patched on the fly once the tank is dry with epoxy or self-bonding metal alloys. The loss of fuel is potentially expensive, especially given a $10 patch... or a $100-$200 welding job by a shade-tree mechanic, and more for a proper heavy equipment repair shop. Hit the engine block? may in fact kill the engine, and not even that month...
The average effect of a .223 Remington/5.56mm NATO to the clothed unarmored chest is a potentially lethal bleed and a roughly 30% one shot stop chance; the end results without body armor have varied from lodged in a bone with little to no significant bleeding (a dozen cc or less) to an aortic dissection and near instant kill, with sufficient shock effect to render the individual incapable of response with force. Given that few games get more detailed than the Chaosium and GW set (Head, Chest, Abdomen, 2×arm, 2×leg), and most only track location for armor, not wounds, random damage after penetration does make perfect sense.