Theoretically, a 1 shot zero is virtually impossible unless your rifle shoots 5 shots in .010"s or under. That shot needs validation.
I hear, my rifle shoots under 1 moa, I ask how do you figure a zero? I understand shifting center of group to aimpoint, but subsequent shots are still high left and low right.
In 1984, I bought a Win 70 Featherweight 25-06, owner of BND sports here in town boresighted it for me, most likely the old Bushnell system. I grabbed a couple of the old Redfield targets, still in use today under all kinds of names, and a couple boxes of Federal Premium 117gr Sierra soft points and headed to the range.
Setup at 100, knowing I want to shoot this barrel cold. I fire one, felt good, could not find the bullet hole on paper, 2.5-8x? Leupold Vari X III. I walked down to the target, low and behold I literally centerpunched the big center diamond, my aimpoint, of course I was in disbelief. I contemplated just packing it in, then realized the goal was 1.5" high at 100 and according to wives tales, now dead-on at 200.
This is when the rodeo started.
It is a name for it. Not reality. I understand you need to validate your zero with subsequent shots.