content staging – How to delete/unschedule scheduled updates for product programatically in Magento 2 commerce edition?

The interface you mentioned is correct, but there is much more useful information inside the model MagentoCatalogStagingModelProductStaging.

In that model, we see the function unschedule() defined as:

/**
 * @param MagentoCatalogApiDataProductInterface $product
 * @param string $version
 * @return bool
 */
public function unschedule(MagentoCatalogApiDataProductInterface $product, $version)
{
    return (bool)$this->entityManager->delete(
        $product,
        (
            'store_id' => $this->storeManager->getStore()->getId(),
            'created_in' => $version
        )
    );
}

After looking at my own instance, I see that all the created_at values in the database are set to 1, I don’t personally use the schedule update feature but it would seem that you would add 1 to the version when running schedule().

I would recommend you open the model/controller for the scheduled updates page and see if you can get any more information about how the versioning system works from there next.

Edit:
Another file that seems to get closer to the answer you are looking for is MagentoStagingModelEntityUpdateActionDeleteRemoveAction.

In it, it passes $this->versionManager->getVersion()->getId() as the version where versionManager is a MagentoStagingModelVersionManager.