No, there’s no real way to prevent this as it has to eventually be in a format that WebGL can render. The GLB is also just model and animation data, no materials or textures.
Some users have tried to make it harder to just copy by encrypting the data and decrypting it client side.
See This is how I protect my 3D models and Why can't I find the glb file in this link?
Generally, it doesn’t matter that much whether someone can download the assets or not as realistically, what can they do with it that’s going to provide a benefit to them? It’s all copyrighted and protected under International law.