WASM and WASI are two different things. WASI is the WebAssembly System Interface.

https://github.com/bytecodealliance/wasmtime/blob/main/docs/...

WASM is targeting web.

WASI(https://wasi.dev/) is the system interface.

WASI is an interface similar to libc - it's a compilation target in place of OS (whereas Wasm is the binary format itself).