You may have brought in your title blocks as block files in the past, and the custom fields updated successfully.
You're wondering why they are not updating when you bring them in as Xrefs.
You'll need to add a custom field in the Field dialog box to match the field your office has created using the DWGProps command.
In this example, we'll be updating the Project Number field from a title block.
With the Sheet Set Manager, you can manage drawings as sheet sets.