If your account is upgraded, your account is upgraded.

Also, how can Avis tell whether your card on file with which you pay for all rentals is a World Elite MC card or just an ordinary MC if you register it in advance (that how it works with Avis Preferrred Elite) and they never look at it? The only indication that a card is World Elite is right above the MC logo. (We know there's nothing in the account number because Citi often upgrades AA Plat MC from World to World Elite without changing the account number a single bit.)

(If think about these issues, I think you'll have your answer.)