The problem is that the figure in question (when combining 1MOA and 2MOA) is not 2.999999 MOA, it's about 2.24MOA. 2.24MOA is significantly different from 3 MOA--especially to someone who's concerned with precision.
Except when you test your free recoiling rifle and ammo with a 30 shot group and it's 2 MOA then dry fire 30 shots from prone and their call plot's 1 MOA, you can well count on the groups you shoot from prone will actually be larger than 3 MOA. Possibly 3.5 MOA.
Go do the statistics on that to explain why that's reality.