Well it is correlated with being a recent CS grad, just like, for example, knowing that d(sin(x))/dx = cos(x) is correlated with being a recent math or engineering grad.

But that's certainly not what it actually measures, which is basic knowledge about data structures. It just so happens that being a recent CS grad is statistically correlated with knowledge about data structures.

But it's certainly not a necessary condition. I am not any sort of CS grad, recent or otherwise, and I still know how to implement a linked list, because I learn things on my own, and refresh my memory about things I forget over time.