That's because the cost center is visible in EKKN table in development server.
Whatever you can see in ME23N - Accounting assignment tab, you can see the same in EKKN table.
Generally in standard, the cost center field is not filled for the account assignment category A. and also cost center filed status is display for account assignment category A (in standard).
As of my knowledge, there are no standard settings to fill the cost center automatically for account assignment category A and it is behaving correctly in your quality system. I guess there must be some custom development / enhancement is working in your development client, that's because the cost center is coming in PO - Account assignment tab.
