If that is true, then TFA seriously missed the mark:
> Alongside the changes in browser styles, page auditing tools like Lighthouse now flag cases of <h1>s without defined font-size as bad practice.
Then when listing what to expect:
> Lighthouse will flag a warning if <h1> is used without a specified font-size.
And under the section "Fixing the Lighthouse warning":
> Lighthouse has recently inherited a check based on Chromium's DevTools warnings for sites that don't specify a font-size for <h1> elements.
Then it uses top-level h1 selectors in its examples of recommended styles. I mean you might be right about when that warning will appear, but the article doesn't seem to think you are.
The example in the article
<body> <h1>Level 1</h1> <section> <h1>Level 2</h1> <section> <h1>Level 3</h1> <section> <h1>Level 4</h1> </section> </section> </section> </body>
can become
<body> <h1>Level 1</h1> <section> <h2>Level 2</h1> <section> <h3>Level 3</h1> <section> <h4>Level 4</h1> </section> </section> </section> </body>