Great questions Andy!

We do support wrapping payload types of any kind because we invalidate _all_ objects returned from a mutation. For example, if you run a mutation like editUser { user { id posts { id } } } we will invalidate any cached query result that contains that user and any cached query result that contains any of those posts!

You are right that smart invalidation can never be 100% reliable, which is why we have the Purging API to manually purge records you know changed from your backend. I think most customers are going to use the manual Purging API, however we also have a bunch of customers with use cases for whom the smart invalidation suffices.