dessa página - "Esse software é baixado automaticamente quando você usa o Assistente do Boot Camp".
..ou você atualizou para o Win10 antes do Boot Camp 6 estar disponível?
Extraia da página que você vinculou (renumerada) ...
- Start your Mac from the version of Windows you currently have installed.
- Open Apple Software Update for Windows and install available updates, including the FaceTime Camera Update.
- Use the Windows installer to upgrade Windows.
- After installation is complete, open Apple Software Update for Windows again and install available updates to make sure the Windows Support Software (drivers) for Boot Camp are up to date. As part of driver installation, your Mac might restart one or more times.
After driver installation is complete, log in to Windows to begin using Windows 10 on your Mac.