Huh? Web assembly is a stack machine and locals do not pose a problem whatsoever.
Yes, the author just needs more work to be done. But it's perfectly doable, although it has a complexity. Like everything in the world of compilers. There are no free lunches.
Yes compilers are hard, but why make them harder? There is literally no reason to require rebuilding this information. The compiler emitting Wasm has that information and already uses it, having locals and disallowing blocks to take/return values actually means more complexity in both the compilers generating Wasm and the runtimes generating native code from Wasm. That's the entire premise of the article.
Even if carrying that information was the thing that you needed (I don’t think it is but there’s a separate thread about that), it’s definitely not the thing that other implementations need.
Yes, the author just needs more work to be done. But it's perfectly doable, although it has a complexity. Like everything in the world of compilers. There are no free lunches.