How does this solve the problem of both governments and corporations wanting to implement this in ways that allow them to hoard datasets?

As it stands, the government in the US uses an identity verification vendor that forces you to upload videos of multiple angles of your face, enough data for facial recognition and to build 3D models, along with pictures of your ID.

I use Tor, so I get to see how age verification is implemented all over the world. By large, the process almost always includes using your government issued ID and live pictures/videos of your face.

There are zero incentives to implement zero knowledge proofs like this, and billions of dollars of incentives to use age verification as an opportunity to collect population-wide datasets of people's faces in high resolution and 3D. That data is valuable, especially for governments and companies that want to implement accurate facial recognition and who have AI models to train.