Should `TIMESTAMP` be required when publishing nightlies

There is a conflict between two parts of the process.
In the refactor release tool job it says `Optional timestamp to add for nightly builds.` against the description of the `TIMESTAMP` field
But if you try to run without a TIMESTAMP set the job says `Nightly must have a TIMESTAMP set`
Is it optional, or is it mandatory? Either way, the messages need to be consistent with each other.