"The app's engine will use result caching so that each statement should be executed either zero or one time."

This isn't true/safe.  The CQL results will not only be dependent on externally retrieved data.  They can also depend on the answers to questions.  For repeating or nested questions, the same CQL may run multiple times, each time with a different context.  Also, if the answers to any questions on which the CQL is dependent are revised (user edits pre-populated data or decides to go back and change their answer), then the CQL will obviously have to be re-run.

Please replace the erroneous statement with a section that talks about dependencies and in what circumstances CQL will need to be re-run.