The drivers are not enabling Crossfire in Fallout 4.
I have done a complete DDU wipe and re-install of Crimson (after the initial upgrade didn't even detect FO4). Crimson now detects FO4, and the CrossFire mode is set to default, however there is no utilization on the second GPU. There is no AMD pre-defined profile available to select for FO4 if I attempt to select it manually. CrossFire is working correctly in all other games, including Rise of the Tomb Raider.
As I said, I did a full wipe and re-install. I have also uninstalled using the AMD install software and re-installed. I have uninstalled and installed Fallout 4. For the heck of it, I did a clean Win10 install, clean driver install, and Fallout 4 install.
I am using the latest (February 4th) hotfix Crimson drivers. I am using the current 1.3 version of Fallout 4.