As far as I am aware, AMD doesn't support AMD Drivers on Windows Preview OSes.
You need to go through Microsoft own link to upload your issues with AMD drivers in Windows Preview OS.
Once the Windows Preview has become official and available to the Public then AMD will support the drivers.
My opinion is that Windows Preview is the same as a BETA or ALPHA program. So whatever issues you are having it is difficult to know whether it is because of the Windows being a BETA and buggy OS which is causing the problem or it is a buggy AMD driver.
I imagine that AMD does test out their drivers in the Preview versions but doesn't support it until the Preview becomes Official.