My usage of the word "production" was a bit non-standard here, in case that confuses you.

Normally, it's used for hosted services, where you have the three hosted environments "development", "integration" and "production".

In this case, I'm guessing, it's rather the case that they had a build configuration for running it in their "build-env", so probably a CI/CD runner. And then there would be a different build configuration for when they're creating a release distribution.

In a very abstracted sense, the "production" environment is where you roll out your release distribution to, so if you will, my laptop is one of thousands of production environments for this application, but only tongue-in-cheek...