Retention Label when defined as record don't allow change metadata
When define a Retention Label as a record don't allow to change metadata (columns) in SharePoint. Now it only not permite change a file, but we can change metadata related to the file in document library.
David Drever commented
I agree. Metadata is used to describe the content. This to me means that it is part of the content and should be maintained just like the document is.
This is highly demanded for unified retention!