Much of the hype around SDD is really about developers never having experienced a real waterfall project.

Of course SDD/Waterfall helps the LLM/Outsourced labor to implement software in a predictable way. Waterfall was always a method to please Managers and in the case of SDD the manager is the user promoting the coding agent.

The problem with SDD/Waterfall is not the first part of the project. The problems come when you are deep into the project, your spec is a total mess and the tiniest feature you want to add requires extremely complex manipulation of the spec.

The success people are experiencing is the success managers have experienced at the beginning of their software projects. SDD will fail for the same reason Waterfall has failed. The constant increasing of complexity in the project, required to keep code and spec consistent can not be managed by LLM or human.