I think such an element would be welcome, and make it easier to add 3D elements to websites. A while ago I wanted to share some 3D models with people, but there weren't any good options. I found a couple sites that lets you upload .obj files, but you need an account and they worked by embedding renderers in iframes. If 3D models had better browser support I hope there would emerge some sites that would let you upload and share them as easy as regular images now.
I don't think it's stranger than having a video tag even though we could embed video without it previously. Having a dedicated 3D tag would make websites more semantic. Hiding stuff in canvas tags like Googles Flutter is the wrong way to go, so bringing stuff out of canvas tags when possible should be encouraged.
Edit: I also think this can be compared to the svg tag. Sure, you could use canvas and webgl and render a 2D vector image using some javascript library. But with svg, you don't have to, and you can style it with css etc.
I don't agree with the tag name though. IMO, "model" is a singular 3D object. Such a tag should support scenes with multiple objects in them.