That completely contradicts itself. If you want to know what the dispersion is, you have to shoot the shots. That's it.
Man, listen, i really can't believe there are 3 pages about this totally obvious topic. Isn'tmy point obvious? So, let's try again. with your reasoning no one would know what the dispersion of his rifle is unless he shoots a 10k rounds group. With 2 or 3 3-shots group i have a very good idea (idea!!) of the accuracy of my rifle with a given ammo. To get the zero and test it at various distances, after i choose the ammo basing myself on my very small and totally useless e shots groups, i have plenty of shots to get confirmation of what approximately is the accuracy of my rifle. After this process i go hunting and, while you discuss about why that 9th shot went 0.2 inches higher than what your calculations predicted, i have already taken a deer and made it meat for the freezer. 10 shot groups are not practical, at all, for a hunter. If you have time and ammo to waste cause you get only one or two tag every year, cool. Spend them shooting in the field from field position or work on your stalking skills.
If i had to do some competitions where it is possible to have to shoot many rounds in a row, i would be more concerned about the rifle's behaviour in fire strings. Otherwise shooting a total of 21 rounds divided in 7 3 shots groups or shooting 21 rounds in a 21 shots group makes no difference, assuming you let the barrel cool down similarly.
Actually i think that 3 shots groups are even better cause you are gonna change target and therefore position so you can have a feedback over how good you are to go behind the rifle in the same way everytime. And then, who cares about being able to put one hole in the other hunting. It's the first shot (cold bore but, more importantly, cold shooter) that count.
I have never followed rules, if a gun shoots very well, you can see it, you don't need many shots to see it if you are confident you are shooting the gun well. Guns are very reliable in priducing their dispersion cone typically. If a gun or load has fliers that sometimes go completely off, the gun or the ammo will disappear from my cabinet ahah