Updates to Supplier Item Catalog

Hello All,
We're making changes to the Supplier Item Catalog whcih are not showing up when raising new Requisitions and or Purchase Orders. I believe this is a "as designed" behaviour as we have outstadnin POs on the system and the chnages won't appear until those open orders have been Closed. Is my understanding correct? If not, what do I need to do to remedy?

Thanks.