There's no such thing as a truly "cross-platform" build. Depending on what you use, you might have to target specific combinations of OS and processor architecture. That's actually why WASM (though they went with WASI) is a better choice; especially for libraries, since anyone can drop it into their environment without worrying about compatibility.
I think GP's point is that instead of having 3 target-specific rust-built binaries, they have 3 target-specific node binaries running rust-built wasm plus wrapper code.
