This was just for WireGuardNT, the kernel driver for the NT kernel that Windows uses.

This project -- https://git.zx2c4.com/wireguard-nt/about/ -- is used by this app -- https://git.zx2c4.com/wireguard-windows/about/ . The former is what the signing situation was about. The latter is just signed using a normal boring (but very expensive!) EV code signing certificate from one of the CAs.