Lighthouse flags pages whose width isn't equal to the width of the viewport:
The audit fails if
window.innerWidth does not equal
In the Lighthouse report UI the full PWA badge is given when you pass all of the audits in all of the PWA subcategories (Fast and reliable, Installable, and PWA optimized).
This audit is a roundabout way of determining if your page is optimized for mobile devices. See Google's Responsive Web Design Basics for an overview of how to create a mobile-friendly page.
You can ignore this audit if: