You’re right that the syntax was inspired by the desire to avoid nested structures. But the syntax here is interesting as well and fairly readable. Worth thinking about!
that example syntax is loosely based on CDK code for AWS Step Functions, since I had to write some recently
essentially you're building a DAG so it could be worth checking some other APIs which do a similar thing for inspiration
e.g. it looks like in Airflow you could write it as:
chain(llm, decider, [agentOne, agentTwo], workflow)