That introduces a level of indirection between "what I want" and what gets built. A workflow like the OP just has less friction. SaaS platforms would want to provide more stable accessible APIs if it becomes a popular model, because users would find it more usable.

these embeddable UI could be a direct ask on how users want a workflow, the SaaS vendors can distribute the embeddable UI and see if it clicks with a lot of users. Would push them to create a stable API