Absolutely, a 1 MOA shooter + a 2 MOA rife will produce, on average, a 2.24 MOA group.
And the biggest group will be 1 + 2 = 3. 3 MOA. This happens when all the errors or variables add up directly.
If all the errors for a given bunch of shots cancel each other out, the smallest groups will be zero MOA. Or close enough to not matter.
Ain't math great?