This is essentially a complete fabrication. If it's on public repo, ready or not, someone will use it for prod.

It's not a fabrication it's a statement that if you use this in prod and it catches fire, that's on you buddy.

This is like saying laws around seatbelt wearing are a fabrication because some people ignore them..

Fabrication means lie. What are they lying about?

That it's not ready for prod when it's a public repo in GitHub

Why does the code being public mean it is ready for prod? I feel you have a large misunderstanding.

Code being ready for production has nothing to do with code being shared privately nor publicly.