This is a knowledge test of GPU architecture?

Kind of, but not any particular GPU.

The machine is fake and simulated: https://github.com/anthropics/original_performance_takehome/...

But presumably similar principles apply.

It's a test of polyhedral layout algebra, what NVIDIA calls CuTe and the forthcoming C++ standard calls std::mdspan.

This is the general framework for reasoning about correct memory addressing in the presence of arbitrary constraints like those of hardware.