In my case, "the business" (executive team) has broad overarching ideas. The PM then works out the specifics, works with UX to design the screens, put together

In my case, "the business" (executive team) has broad overarching ideas. The PM then works out the specifics, works with UX to design the screens, put together the copy, talks to engineering to understand what technical challenges may exist, then works with individual teams to break down the high level into small specific tasks. During development, they manage our todo column, answer questions, help make adjustments when previous assumptions prove false or we run into unexpected challenges, etc. As an engineering manager, I've actually found it quite helpful.