> I don't see how AI would help with that

What if the AI kept bringing up unspecified cases and all you (the human) had to do all day was respond to it on what the behavior should be in each case? In this model the AI would not specify the outcomes; the specification is whatever you initially specified, and your responses to the AI's questions about the outcomes. At some point you'd decide that you'd answered enough questions (or the AI could not come up with any more unspecified cases), and bugs would be in what remained, but it would still mean substantially more thinking about cases than now.