In the repro the capsule cast is so tiny, why can't a raycast be used here instead?

In the physx docs it says:

"There are some pitfalls to be aware of when using sweeps:

Due to numerical precision issues, incorrect results may be returned when the objects have very large size disparities."

This is clearly what is happening here, reducing the size of the massive massive plane fixes the problem.

We will update the Unity docs to reflect this.