Unexpected system behavior when Allow Description Update flag in item master is set to No

After upgraded from R12.1.3 to R12.2.7, we find that the item description saved in po_lines_all is no longer being used to display on the PO form. The PO form display item description directly from item master. If there is item Master Update, All item description of historical PO / BPA will become mismatch when buyer reviewing the PO via PO form.

This behavior is really confusing buyer who has send PO to supplier with Item description A but it become item desriptoin B when checking on screeen.

In addition, we find that iProcurement is keep retrieving the item description of po_lines_all instead of from item master