sigh.. it doesnt matter if Polaris or even Vega "uses"/supports DX12.1 or dx13 or dx195...
simply because its up to the application you use, not the gpu, if a game doesnt support DX12 it literally doesnt matter if your GPU does or not, the GPU wont perform worse/better because of it in that application,
it will/can only improve in an application that actually uses DX12
so if a game doesnt even use DX12.1 features (which many currently dont and prob wont for a long time thank you consols) it has no direct impact on the GPU hardware performance
and since Nvidia already supports the features its a mute point to use that as comparison tool, even if DX feature mattered
what will matters most is the direct hardware capabilities, which for Polaris, and Vega are mostly speculation at this point, until we get the cards in hand and can compare them directly in test against Pascal
Nvidia isnt releasing "early" because they are threatened by AMD. The launch was always supposed to happen before AMD, only the specific date was in question, what reasoning AMD has to launch later is another matter. more testing, working out some kinks, strong quality control? feel free to speculate. in end then only the end result will matter
weather or not Nvidias "brute" force tactic will end up resulting in a better performing card than AMDs architecture we simply cannot know until the cards are in 3rd party hands to be tested and compared
but weather or not a card supports an API feature lvl or not will have no impact on the specific hardware performance, ONLY software performance in software that uses that API. so never let that be a deciding factor when "selecting a winner"
never compare "nvidia dx12/12.1" vs "amd dx12/dx12.1", only hardware capabilities in direct match up tests, until API tests can be made
which again, remmeber DX12 is far from the common standard yet, + we got Vulcan on the rise too
a good example would be AMD and Nvdia both supported dx12, however neither "truly" supported 100% of dx12 features,
AMD architecture just meant that their latest cards benefited strongly when used in combination with dx12 api, despite Nvdia cards also supporting dx12., and the same cards had reverse results when tested in dx11 api
so you cannot speculate on which is stronger in a purely software bound performance until the actual tests are out.