First - they are not identical. You can't install a video driver for Windows on a Bootcamped Mac. For AMD drivers, you will get an error if you try using the Windows installers. Must be a Bootcamp happy driver installer.
After days on the phone with Apple, Apple flat out INSISTS that AMD handles the Bootcamp drivers.
Conversely, if you speak with AMD, AMD flat out INSISTS that it's Apple who supplies the drivers to AMD for bootcamp.
Don't take with issue with me on this, call them both first. Trust me. After multiple tries with different levels and departments with both Apple and AMD, they will literally leave you where Apple points to AMD, and AMD points to Apple.
Wonderful little relationship the two of them have. Meanwhile, customers can't play certain games on their still very powerful iMacs, because we can't get an up to date video driver for our systems. There are new Windows drivers, that work fine on Windows hardware. But, because Apple won't let us install windows graphics drivers on their hardware, we have to wait for ... Apple? AMD? Dunno which... to get around to drivers that will be out of date already when they get released.