i figured out the issue—i changed the release date from a specific date to an estimated date, resubmitted for review, and it was approved (estimated date does not require a binary). i was able to push to live after that, which published the store page as “coming soon.”
this is in the documentation, but it would have saved me a half-dozen failed reviews if this had been included in the review feedback: https://dev.epicgames.com/docs/epic-games-store/store-presence/manage-offers#dates