A user adds annotations in the Exported Annotation file, then the file is imported by another user using the Imported Annotation action. In the document, the author of these annotations is replaced by the user who performs the Import Annotations action from UI.
Exported Annotation File:
Annotations Imported in Document:
Why is not the original author reflected in the document?
It is working as designed.
When a user imports annotations, that user becomes the author of each resulting Vault annotation.
Vault Help Documentation: N/A