I think the need or the advantage of the DID and DSD is that they serve two different audience. DID, which contains the broad specifications, is great for the customers, the ones who are actually interested in buying the product. It is also good for project managers, to review the market needs and the importance of such a product. This audience doesn’t need to see or know the exact specifics of dimension, color, etc. Just the overall purpose and design of the product.

The DSD on the other hand, contains the highly detailed specifications, this is needed for the internal team of research and engineers. It helps them design the product well, having every aspect specified. It also helps during testing and risk management. The DID can’t be used for such significant development and testing.