tldr; I’m just going to say right now that the dialog element and its polyfill are not suitable for use in production. And it’s been that way since the dialog’s earliest implementation in Chrome, six-ish years ago.
Eliminate risk and deliver value using feature management in your development cycles. Deploy code when you want. Release features when you're ready. Control your users' experience.
Many of the components we design for the web are made to save space. It’s interesting that we work so hard to save space on a medium where we have infinite space to work with.