No need for such an element. It's such a private use case to display 3D models that it's better suited as a web component than an element in the standard. See for example <model-viewer> https://modelviewer.dev/
As others have mentioned, the privacy implications are much more important. That is, the site owner will not have to have access to eg. the camera stream, but still use AR with this method.
So in a way, the value in this proposal is that it is less capable than the from scratch approach, and can be implemented safely just in the browser.