There was a time when support for DirectX 12 on Windows 7 would have been a big deal. In 2015, for example, when it launched alongside Windows 10. Embracing the 'better late than never' adage, Microsoft has finally "decided to act" on feedback imploring the company to bring DX12 to Windows 7.
By "act," Microsoft means it's working with a select group of developers to port existing DX12 games to Windows 7. The first (and so far only) game to gain DX12 support in Windows 7 is World of Warcraft, enabled with the 8.1.5 patch. Or put another way, a game that is around a decade-and-a-half old is bringing DX12 support to an OS that is reaching end-of-life status. Uh, great?
I'm not sure what the overarching goal is here, at this point. Microsoft isn't exactly opening up the spigot and letting DX12 flow freely to Windows 7, and barring a stay of execution, it's planning to end support for the OS on January 14, 2020 anyway.
That said, there will be a few more games added to the fold, presumably between now and then. "We are currently working with a few other game developers to port their D3D12 games to Windows 7. Please watch out for further announcements," Microsoft says.
DX12 is a low-level API that can ultimately enable developers to deliver faster framerates in games. As Microsoft points out, however, Windows 10 is still a better match for DX12.
"Windows 7 WoW gamers can run the game using DirectX 12 and enjoy a framerate boost, though the best DirectX 12 performance will always be on Windows 10, since Windows 10 contains a number of OS optimizations designed to make DirectX 12 run even faster," Microsoft says.
Limiting DX12 to Windows 10 was one way Microsoft was able to push users (and gamers in particular) to upgrade. Now several years later, Microsoft says there are 800 million Windows 10 devices in the wild, hence one reason it is finally loosening its grip on DX12, even if just slightly.