When Heading Structure Breaks, Navigation Breaks With It

JAWS screen reader output on the Dupixent website showing all headings detected as heading level 3 with no H1 or H2 present, demonstrating a broken heading hierarchy.
<h1>Brand Name</h1><h2>About the Treatment</h2><p>Overview content here.</p><h2>How It Works</h2>  <h3>Mechanism of Action</h3><h2>Important Safety Information</h2>  <h3>Common Side Effects</h3><!-- H1 → H2 → H3. No skipped levels. -->