It would be generally good if most code made setting up such tests as easy as possible, but in most corporate codebases this second step is gonna require a huge amount of refactoring or boilerplate crap to get the things interacting in the test env in an accurate, well-controlled way. You can quickly end up fighting to understand "is the bug not actually there, or is the attempt to repro it not working correctly?"

(Which isn't to say don't do it: I think this is a huge benefit you can gain from being able to refactor more quickly. Just to say that you're gonna short-term give yourself a lot more homework to make sure you don't fix things that aren't bugs, or break other things in your quest to make them more provable/testable.)

That is an unfortunate case you described, but also, git gud and write tests in the first place so you don't need to refactor things down the road.