I'm not sure you understand how it works. Nvidia no longer train specific games as their AI model for motion-based image reconstruction is now seemingly advanced enough that it is game agnostic. That tech is proprietary and Nvidia use it as a selling point for their RTX GPUs, taking advantage of the Tensor cores to accelerate it.
Game devs can't simply "use" directML to achieve the same thing. There's no models available for them to utilize, Nvidia aren't about to release their DLSS model for everyone to use. Could each game dev hire some AI model programmer to train for their game and provide that to directML for any GPU drivers that support it? Sure. I can't see that happening much though, outside of some tech experiments by large publishers.
Hunh...?
No, I don't think you understand. NVidia doesn't make games. And they can't pay every developer to use their model, and NVidia can not AI every game. Otherwise, in over 20 months of DLSS and Turing, we would have more than 6 games..!
So, NVidia has already proven, that they are incapable of doing it for each game (DLSS 3.0 remains to be seen). But if you read the article you will see that Microsoft is using Azure to train AI models in near instant.
Lastly, I do NOT see Game Dev's catering to 5% NVidia owners with $1,200 cards.