Uncharted 3 sold 12.17m then. If you're going to include the trilogy sales for GOW 3 then it's only fair to do the same for Uncharted...
But the Uncharted Collection was on PS4. A platform where Uncharted 3 never was available before. And it included two other games (Uncharted 1 and Uncharted 2) which where also new to the Playstation 4. God of War Saga released on PS3, a platform where God of War 3 had already been available. And both God of War 1 and God of War 2 were also already available on PS3 with the God of War Collection. So basically God of War Saga targeted a much smaller audience than the Uncharted trilogy on PS4.
But I see your point, it's just a matter of how you want to compare both of them.