Wasm is a first-class target for Rust, which produces faster and smaller Wasm binaries. My understanding is that you need to use TinyGo to reasonably target Wasm with Go.

Go having a garbage collector isn't necessarily bad, since Wasm has GC, but I think Go's GC can't easily use Wasm GC because Go has interior pointers.

I think the main advantage is size. Rust doesn't need to include the runtime.

I'm assuming they mean because it doesn't need a garbage collector or much of a runtime at all. You can target direct to WASM and use I guess WASI, while Go brings with it a garbage collector and so on.