What likely occurred if a requirement appears between the product requirement and detailed design documents?

If a requirement appears between the product requirement and detailed design documents, this often indicates that the development team played a significant role in its addition. During the transition from product requirements, which outline what the product should do from a high-level perspective, to detailed design documents that specify how those requirements will be implemented, it is common for the development team to identify technical necessities, constraints, or changes needed to meet the initial product requirement.

This often happens as the development team assesses how to translate high-level concepts into practical implementation. They may introduce new requirements to address technical challenges, ensure feasibility, or enhance the overall performance and reliability of the product. Therefore, the presence of such a requirement signifies that the development team has actively engaged in refining the requirements to align with what can be realistically built, thus ensuring a more seamless development process.