What would you use this for? I don't get the whole picture and the article doesn't talk about it.
In practice, this means that you can compile your Rust/C++/etc code to WASM + WASI, and that code will run anywhere you have a WebAssembly VM. So the same code that accesses the "filesystem" in a browser context can also access the filesystem in a desktop/mobile/edge/etc environment.
You could also think of it as an attempt to turn WebAssembly into a fully-fledged JVM alternative. Compile once, run anywhere (including browser).
For this specifically, it means that SQLite can integrate with WASI APIs (instead of only Web APIs as before) so that an SQLite Wasm build can run in other contexts besides browsers.