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.

Start by locating the refactor release tool job and the TIMESTAMP validation mentioned in the issue. Compare the field description with the nightly error message and determine the intended requirement; done means the validation and user-facing descriptions consistently reflect whether TIMESTAMP is optional or mandatory.

Written by the indexing model from the issue text.