title: Preloaded css file containing nothing but comments still affects Largest Contentful Paint
body: <p>I have been trying to understand how to optimise the LCP for my website.</p>
  <p>At the start my LCP is 2-3 seconds with my css file included, and under 1 second without it.</p>
  <p>Following <a href="https://web.dev/defer-non-critical-css/" rel="nofollow noreferrer">https://web.dev/defer-non-critical-css/</a> I preload my css file, and inline my critical styles.</p>
  <p>This is how I preload my styles:</p>
  <pre><code>  &lt;link rel=&quot;preload&quot; href=&quot;/static/style.css&quot; as=&quot;style&quot; onload=&quot;this.rel='stylesheet'&quot;&gt;
  </code></pre>
  <p>This had no effect whatsoever on the LCP reported by lighthouse.
  At this point, just to make sure there were no hidden &quot;critical&quot; styles in my css file, I replaced the content of <code>style.css</code> with 20k lines of comments.</p>
  <p><strong>Preloading this 20k comments file caused my LCP to be 5 seconds!</strong> &quot;Time to interactive&quot; was also five seconds.</p>
  <p>What the hell is going on!? How can a preloaded css containing nothing but comments possibly affect the LCP time? Obviously it does not really change the rendering time of the actual content of the viewport.</p>
  <p><strong>EDIT:</strong>
  This might actually be <em>caused</em> by the simultated throttling in Lighthouse</p>
  <p>This Image shows simulated throttling OFF. You can see the LCP is well before the theme finishes loading.</p>
  <p><a href="https://i.stack.imgur.com/obTHa.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/obTHa.png" alt="enter image description here" /></a></p>
  <p>And here the only difference is that I turned simulated throttling ON. You can see the page isn't rendered without styles at all, and the FCP and LCP are well after the css (purple) is downloaded.</p>
  <p><a href="https://i.stack.imgur.com/w82Jf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/w82Jf.png" alt="enter image description here" /></a></p>
  <p>Is it likely that Lighthouse is giving me funny results?</p>