In QA, there is a distinct moment. It comes once you're deeply familiar with your product or product area; it comes when you're lost in your testing, and it comes in an instant. You find a problem, and because of your strong context about your product, you definitely know: Something is seriously wrong here.
I learned today that the root causes of a HTTP 404 response in one of our applications are not distinguished at all. Thus, the team literally has no idea which one of the causes is the underlying issue. I don't need strong product context to know that the ability to detect failures and the ability to understand failures is the most important part of software development. Good software without a good QA mindset isn't good software.