Now on 1903 and see same, suspect this is a gpu-z read issue with 1903.
Might be an idea to report it on their forum.
Maybe the Dev needs to update the Dec.'18 vers. for 1903 ?
Of course also report it to the amd driver team using 'Report Issue Online'.
I have one game that I loaded up and the OSD said VULKAN
Wolfenstein II was such a game
Game was working ok at 3840x2160 when testing games
I have also tested my Vega 11 for several games but it is not as powerful as my GTX 1060 for some demanding games
it's not the driver the problem is from windows 10 1903
There was a smallish update today for 1903 but I suspect more updates are pending to be delivered soon
AMD has been cranking out updates regularly so they are trying to stay on top of things