The problem with planning and specifying in excessive details is that it’s not what we think we know, but what we don’t know that we don’t know and how we handle it when we find out that decides the predictability of the projects we are working on.
Details are good as such – but they rarely secure predictability.
Big or small, detailed or high-level – user stories and requirements are just proxies for what we think we know. Cannot be trusted to secure predictability and success.