No. WSL2 is a Linux VM. It doesn't expose Windows API internals or implementation details. It uses normal, already well-documented public ones. Wine and ReactOS can already use the publicly available documentation and they are still behind on many such APIs' implementation. Windows is a big OS. It takes serious man power to implement many things.

Probably not. WSL2 is a kind of a VM, so it should be bypassing the Windows API.