Invoices can be approved even if there is no distribution coding entered

Summary

Why does the system allow invoices to be approved even if there is no distribution coding entered

Content

Currently we do not provide non AP users to enter the distribution coding.  When Fusion sends the invoice approval email, the guidance is to reject and provide the coding if not present or approve when already present.  However, we have many users that approve even when there is no coding present. 

Why would fusion allow approvals when there is no coding?  Is there a way to prevent this?

Version

R13 20D