Commercial DD analysis too late?

As I was watching the Commercial DD course, I was wondering if many of these analyses were not too late in the process. Ideally, many of the topics raised would have already gotten attention when the deal was being discussed in the strategy rationalization of the deal. I understand there will be new information and access to management but curious to see how much of this analysis is “new” and how much of this is “validation” of previous work before the DD already started