[i18n] explicit access to /en not redirecting to /

What version of Next.js are you using?

10.0.5

What version of Node.js are you using?

14.15.0

What browser are you using?

Chrome

What operating system are you using?

Windows 10

How are you deploying your application?

next dev (localhost)

Describe the Bug

According to docs when enabling i18n with following config:

module.exports = {
  i18n: {
    locales: ['en-US', 'fr', 'nl-NL'],
    defaultLocale: 'en-US',
  },
}

only available URLs should be:

/blog
/fr/blog
/nl-nl/blog

but if I try to access page explicitly specifing default locale (i.e. /en-US) then it will show page as is, without being redirected to /

Expected Behavior

It should redirect all paths prefixed with default locale to non-prefixed paths (i.e. /en to /, /en/hello to /hello etc).

I would like to get rid of duplicated pages, because it potentially can bring problems with SEO.

Also, I couldn't fix it using redirects section because it runs into infinite loop (ERR_TOO_MANY_REDIRECTS ):

 async redirects() {
            return [
                {
                    source: '/en',
                    destination: '/',
                    locale: false,
                    permanent: true,
                },
                {
                    source: '/en/:path*',
                    destination: '/:path*',
                    locale: false,
                    permanent: true,
                }
            ];
        },

To Reproduce

1. Download and run official i18n-routing example
2. Try to access to /en (default locale) and make sure it will show page without redirect

Start by running the official i18n-routing example and request the default-locale paths described in the issue, including /en and /en/hello. Compare the observed behavior with the expected redirects to / and /hello; the work is done when default-locale-prefixed paths redirect without creating redirect loops.