I often have my AI code output one just to make sure my logic feels more sound. Along with mermaid charts if I need to toy around or drop into stately for more power.
I've had models produce very reasonable Mermaid diagrams that matched the intended design but not the actual program. It felt helpful until I realized I was reviewing the plan twice and the implementation zero times.
For PRs I'd rather render the diagram from the executable state machine itself — at least then drift in the chart means drift in behavior, and you can't review one without the other.