It does look like Filament has a web target:

https://github.com/google/filament

but if they're targeting embedded systems, maybe they haven't prioritized a public web demo yet. If the bulk of the project is actually in C++, making a web demo probably involves a whole WASM side-quest. I suspect there's a different amount of friction between "I wanna open source this cool project we're doing" and "I wanna build a rendering target we won't use to make the README look better."