This is such an exciting proposal for the web. From what I understand, this would be one of the final hurdles to having WASM "just work" in browsers the way people always expected it to (i.e. having standardized support for directly interacting with Web APIs/the DOM, without any janky glue code and skipping the huge inefficiencies of intermediary JS).
The end result would be developers having a much easier path to implementing huge parts of their applications with native-like speeds in any language they want. Some people will want to do their whole application this way, and others will have specific modules that can benefit hugely from this while still making considered use of the rest of the web platform.
As they say in the article, the current status quo is that this is possible but that ad-hoc/custom WASM modules are out of reach for all but the largest developers because of the cliff of complexity involved in moving beyond the most well-trod paths.