Looks like the missing titles from the Numenera Libraries are now available to those who pledged at the relevant levels. Slaves of the Machine God is now available in the Backerkit downloads (here https://numenera.backerkit.com/backer/digital_rewards for ease of reference). With the PDFs that were missing from the bundles available via the MCG store, these appear to have been added to the downloads section of accounts (or at least they were added to mine). So no need to claim coupons (although if you're eligible for the bundles and haven't claimed the coupons yet, I'm guessing you'll still need to claim the coupons before they'll appear in your downloads). Thanks to the MCG team for resolving the issue.