Some fields are not available to be used in a Vault report with Cross-Version Reporting enabled.
Some fields are not made available when Cross-Version Reporting is enabled in a Vault report.
There are some formula fields that cannot be computed correctly when Cross-Version Reporting is enabled. These fields are restricted from the Report Builder when this feature is enabled in Vault. This is working as designed.
The following formula fields are not available for selection when creating a cross-version report:
Vault Reporting Documentation: Cross-Version Reporting