A lot of the times, the BA gives you wrong business requirements, and an experienced software engineer can see it's wrong by reading it, and refuse to start it until the requirements are fixed. By "wrong", I meant there is a logical contradiction, or there would be harmful logical side effects because the BA can't play out the logic in their head, or it's technically impossible, or the development effort would not be worth it (for example, replicating what Google took years to build as a nice-to-have feature for an internal tool that isn't critical to the business).