I tried the process, created PO from the PR, the PR status tab has the processing status 'PO created'.
The PR line item get deleted when I set the message category for the message no. 06152 as "No Message" and the line item status changed to 'deleted'.
The PR line item not get deleted when I set the message category for the message no. 06152 as "Error"and the line item status changed to 'Warning'
Please re-check the system behavior.