title: Why does Google Lighthouse not count all the DOM elements for its DOM size calculation
body: <p>I am looking into reducing the size of a website's DOM.
  When I run Lighthouse over a page the DOM rightly highlighted as excessive is 1,824 elements.
  When I then go into the console and run a small script <code>document.getElementsByTagName('*')</code> it returns <code>HTMLCollection(2212) [HTML, ...]</code> which is somewhat higher.
  I am assuming either</p>
  <ul>
  <li>one of those two results is incorrect - in which case which</li>
  <li>Lighthouse excludes certain elements from its count  - in which case what</li>
  <li>something else.</li>
  </ul>
  <p>Does anyone have any insight into this?</p>