At the moment, a lot of WASM tooling assumes instances interact with a JS engine. So, we aren't compatible with a bunch of existing tooling, like Rust's wasm-bindgen. We're working on our own tool to fill that hole in the ecosystem.
We also aren't 100% of the way to spec compliance yet. We have a plan to get there, but spent the last year or so putting the bulk of our effort into performance and integration with our edge cloud systems.