I have a very good mental model in my head of each and every codebase I have ever worked on. Nothing to do with my PRs or even my team’s direct responsibilities. I could always direct a thought provoking idea to challenge the existing status quo and get a reasonable nuanced answer from code owners on slack or during a water-cooler talk. I build that mental model also by reading the code. This is my job, so I know when to tear down what or how to respond to a random product idea immediately on a meeting to asses complexity.