safari js func define issue

seems safari defined functions even if they live in conditional blocks

HTML

<!DOCTYPE html>
<html lang="en">

  <head>
    <meta charset="utf-8">
    <title>Safari JS engine test</title>
    <script type="text/javascript">
      if (false) {
        function conditionalFunctionality() {
          alert("Doing conditional functionality");
        }
      }
      window.onload = function() {
        if (typeof conditionalFunctionality === "function") {
          alert("BAD. It's defined");
        } else {
          alert("GOOD. It's NOT defined");
        }
      }

    </script>
  </head>

  <body>
    <h1>Safari JS engine test</h1>
    <p>
      Safari 12 (iOS 12.0.1 and macOS 10.14) incorrectly/unconditionally define the conditional function.
    </p>
    <p>
      All other browsers below pass i.e. the conditional function isn't defined.
    </p>
    <ul>
      <li>
        Chrome v70 on win64, macOS 10.14
      </li>
      <li>
        Firefox v62 on win64, macOS 10.14, linux x64
      </li>
      <li>
        Edge v42 Windows 10 x64
      </li>
    </ul>
  </body>

</html>