The thing to remember is this is in the "Competition shooting" section.
The old saying is three shoots proves the load, Five shots proves the shooter. As mentioned before if you wish to see the full potential of the rifle then shoot a 10 shot group. I don't know of any competition that shoots 3 shot groups, I could imagine that some club somewhere may do it, but generally speaking no one shoots 3 shot groups for competition. So I would agree measuring three shot groups is a waste.