The argument I was making was what is why would

    <main>
    
    <h1>Main Heading</h1>

    section..h2... Etc

    </main>
    
    <aside>
    
    <h1>Aside heading</h1>

    section...h2...

    </aside>

Be incorrect? The original html standard clearly stated this was acceptable but now there should only be a single H1 which is the page heading and all other headings should be H2 and lower. What if the page content doesn't actually have a single main heading? This change fundamentally changes the semantics of something which has had unclear semantics for decades and which actually rendered what I typed above correctly in the past. Now it would not be rendered correctly anymore.