I think Anthropic's definition of workflows is inaccurate for modern definitions of the term. Temporal for instance (disclaimer, my employer) allows completely dynamic logic in agentic workflows to let the LLM choose what to do next. It can even be very dynamic (e.g. eval some code) though you may want it to operate on a limited set of "tools" you make available.
The problem with all of these AI specific workflow engines is they are not durable, so they are process local, suffer crashes, cannot resume, don't have good visibility or distribution, etc. They often only allow limited orchestration instead of code freedom, only one language, etc