That's about right. Specifically, wasm32-unknown-unknown is serving multiple targets, which aren't very compatible, and it implements std by panicking in all the bits that can't work.
One target is "you truly have absolutely nothing, and don't really have much of `std` at all". Another target is "you're in a browser, and can do anything a typical browser can provide" (ideally targeting the future where wasm has full browser APIs without going through javascript). Another target is "hosted environment that isn't a browser, and which capabilities you have depends on the environment". Those are three very different things.
I would argue that we need at least two new targets, possibly three:
- `wasm32-none` or similar (by analogy with `x86_64-unknown-none`), a target where you don't have anything except for what you bring with you. The equivalent of writing kernel code.
- `wasm32-wasi-hosted` (or pick another name), where you the hoster of the wasm can supply whatever capabilities you have available.
- `wasm32-wasi-browser`.
It's possible that `none` could be a special case of `hosted`, where the services you provide are "none".