> Orchestration needs an orchestrator, choreography does not.

That analogy doesn't make sense to me.

An orchestra can play a piece without a conductor.

Choreography has an "orchestrator" for all but the final performance.

Neither can work indefinitely without a director, while both can work for a single performance without a director.

So it's still not clear to me what the difference is supposed to be.

Huh? If you don't have a choreographer, you don't have choreography. You have improvisation instead.