The development of Business Architecture Descriptions is always iterative because it involves constant refinement and validation of the architecture models and views based on stakeholder feedback and changing requirements. Therefore, any Architecture Description that was created in Phase A may need to be updated in Phase B as new information or insights emerge. Phase B does not require that all Architecture Descriptions be updated, only those that are relevant and necessary for the Business Architecture. Phase B is an ADM Architecture Development phase, but that does not explain why Architecture Descriptions need to be updated.
A new value stream may or may not require updating existing Architecture Descriptions depending on its scope and impact.
In TOGAF's ADM, the development of architecture is an iterative process. During Phase A, initial business capability maps and value streams are created to establish the Architecture Vision. However, as stakeholders provide more detailed inputs and requirements are refined, it isnecessary to update the Architecture Descriptions. This is an iterative process that continues into Phase B, Business Architecture, where these descriptions are further developed and refined.