This may be well what needs to change, but in any case the message from Google should have been explicit about it instead of the dev involved having to create a blog post, hope it gets traction on HN and that someone here knows what the problem is.

Yes and no, I would be glad if Google in general could get much much better at this but in this specific case I'm sorry but http://* and localhost access is not a hidden small thing.

the docs are pretty explicit about it

But not their email.

Native messaging is extremely broken and has bad documentation. I never got replies to my bug reports about it and gave up and just used websockets.

Out of curiosity, what were the problems you ran into with native messaging?

So native messaging is fundamentally about opening a named pipe to a child process managed by the browser. I found that the pipe would silently break or time out. In the former scenario, the app was running but could no longer exchange native messages with the browser or extensions - chrome was just ignoring the pipe traffic. In practice I was able to use native messaging to spawn the executable but to actually talk with it I needed to use a websocket, kind of defeating the point.

I initially assumed I was doing something wrong but after a week or so experimenting with simple test cases I could not get it to work. Maybe it works fine on Linux and Mac but not Windows.