Experimental "redirects" feature not redirecting to expected url (missing "query" part)

[Vadorequest]

Using the following innext.config.js

experimental: {
    redirects() {
      return [
        {
          source: '/:lang((?!fr|en))/:path*',
          destination: '/api/autoRedirectToLocalisedPage?path=:path*',
          // Permanent uses 308, otherwise uses 307 - See https://github.com/zeit/next.js/issues/9081
          permanent: process.env.APP_STAGE === 'production', // Do not use permanent redirect locally to avoid browser caching when working on it
        },
      ];
    },
  },

1. When I go to http://localhost:8888/, I get redirected to http://localhost:8888/api/autoRedirectToLocalisedPage, but I'd expect to be redirected to http://localhost:8888/api/autoRedirectToLocalisedPage?path=.

2. When I go to http://localhost:8888/test/some-page, I don't get redirected at all and it displays a 404 page.

Am I doing something wrong? I want that to redirect if the url doesn't start with /fr or /en.

[TommySorensen]

This is apparently out of scope of RFC
#9081 (comment)