Is the ContentBodyId the ContentPack id/reference on the ContentVersion Object?
The official docs, list some verbage that is unclear to me.
"Allows inserting a file version independently of the file blob being uploaded. This field is available for query and insert only. It can only point to a ContentBody record. This field is available in API version 40.0 and later."
It is a reference field, seems logical to be the Content Pack (body itself).