why? it doesn't matter in any non-trivial app

In other contexts people complain about every byte shipped too much but whenever WASM comes up kilobytes of useless JavaScript shims don't matter. And it is one unnecessary extra request we should not need. It is one extra build step to generate the bindings.

How does it? Worst case it adds 1% KB on top (WASM has fairly big binaries in general). The unnecessary extra requests are not performance critical and the programmer doesn't even notice one more build step in the build steps of dozen other pkgs.

Surely it would be nice, but it's not a real deal breaker

Actually, building WASM direct DOM api first, then building the native DOM api as an extension of that sounds like a great idea.

My understanding is that "the DOM API" is specced very much in terms of Javascript, so WASM component stuff might see a "DOM2 API" that's similar but not really the same API. Lots of work in speccing that out, I bet. But yes, please!