The comment about no two people having the same zero is bunk. Take this for what it's worth. My older brother was about as different from me as could be. He was left handed, about 6'1", 250-270#. I'm right handed, 5'9", 150-165#. I sighted his rifles in all the time and he then fired a couple of shots to confirm-into the same group.
Well, if folks do that with apparent succes, I doubt they're able to shoot no worse than about 1 MOA with the sights used. Especially when a couple of shots have less than a 20% chance of represent where the zero's at. If you're both shooting about 2 MOA or thereabouts, it is quite possible that the same sight settings will seem to work.
With a rifle and ammo capable of 1/4 MOA accuracy and both shooters able to call shots within 1/3 MOA of exact, then you'll see the difference in sight settings.