OP jumped the receipting step and printed purchase receiver

A user printed the Purchase Receiver without first receipting the op:

This caused the status to advance, but the amounts remained open:

My question is how did the system allow this to go through?

The Order activity rules are setup:

but the Override Next Status field on the Purchase Receiver print job is Blank:

Where else do I need to check in order to prevent this from happening again?

Thank you