Chrome 58 gives a smaller font size (1.5em, same as <h2>) for <h1> elements under <section> and friends:

  /* user agent stylesheet */
  :-webkit-any(article,aside,nav,section) h1 {
      font-size: 1.5em;
      -webkit-margin-before: 0.83em;
      -webkit-margin-after: 0.83em;
  }

And <h1> keeps shrinking as you nest <section>s. So yes, someone has actually implemented it. (I personally don't like the <article> part, but well -- whatever.)