Required fields not enforced with import of attachments

Document Type of BP - submittal

Several ways to add attachments - Add as line item or import as a line item.

Whenever attachment is imported as line item, the required fields of the line items are not enforced and allow the user to route the record to the next step where the record get stuck and needs to be terminated

Is this a bug or did I miss a check mark or something in the setup?

Thanks

AnitaB