I find it hard to believe that a yearling female is going to become gravid. And a female that's mature enough to lay eggs will lay fewer and the eggs will be less viable (if fertile) the smaller the female is.
For a large nesting area that's connected to the tank somehow, I would think it would improve the chances of it being used as long as a turtle also had privacy. A sense of control (choosing when to go to the nesting box) would be important. I've seen females dig in several areas, not that far from each other, before they settled on a spot to complete a nest.
