I don't think this would have helped us a lot on Go.
We occasionally get reports like "We're seeing [issue] on our system, but only when it's loaded with production traffic." Some bugs are simply impossible to reproduce in an isolated, mechanical way. (Or at least very hard for people who aren't totally familiar with the project.)
But often one of the core will take a look at those reports and say "Aha! That must be a consequence of [some change we made]." Then they investigate, poke at some of their code, check their assumptions, and eventually find the cause.
Another large class of bugs pertains to docs, for which the concept of "reproducibility" is irrelevant.
We occasionally get reports like "We're seeing [issue] on our system, but only when it's loaded with production traffic." Some bugs are simply impossible to reproduce in an isolated, mechanical way. (Or at least very hard for people who aren't totally familiar with the project.)
But often one of the core will take a look at those reports and say "Aha! That must be a consequence of [some change we made]." Then they investigate, poke at some of their code, check their assumptions, and eventually find the cause.
Another large class of bugs pertains to docs, for which the concept of "reproducibility" is irrelevant.