My only guess is they have a parallel skunkworks working on the same thing, but in a way that they can keep it closed-source - that this was a hedge they think they no longer need, and they are missing the forest for the trees on the benefits of cross-pollination and open source ethos to their business.
IBM and Microsoft made OS/2. The first version worked on 286s and was stable but useless.
The second version worked only on 386s and was quite good, and even had wonderful windows 3.x compatibility. "Better windows than windows!"
At that point Microsoft wanted out of the deal and they wanted to make their newer version of windows, NT, which they did.
IBM now had a competitor to "new" windows and a very compatible version of "old" windows. Microsoft killed OS2 by a variety of ways (including just letting IBM be IBM) but also by making it very difficult for last month's version of OS/2 to run next month's bunch of Windows programs.
To bring this back to the point -- IBM vs Microsoft is akin to AMD vs Nvidia -- where nvidia has the standard that AMD is implementing, and so no matter what if you play in the backward compatibility realm you're always going to be playing catch-up and likely always in a position where winning is exceedingly hard.
As WOPR once said "interesting game; the only way to win is to not play."
Windows NT wasn't really relevant in that competition for much longer, only XP was finally for end consumers.
> where nvidia has the standard that AMD is implementing, and so no matter what if you play in the backward compatibility realm you're always going to be playing catch-up
That's not true. If AMD starts adding their own features and have their own advantages, that can flip.
It only takes a single generation of hardware, or a single feature for things to flip.
Look at Linux and Unix. Its started out with Linux implementing Unix, and now the Unix are trying to add compatibility with with Linux.
Is SGI still the driving force behind OpenGL/Vulcan? Did you think it was a bad idea for other companies to use OpenGL?
AMD was successful against Intel with x86_64.
There are lots of example of the company making something popular, not being able to take full advantage of it in the long run.