Sounds like a bluff. American Express could do this, but we have no reports of it for USA-issued cards. In Canada there does seem to be an adjustment made if their $200 credit (which is different) has been used.
Thank you, I think she was bluffing too. I was polite but insistent that I didn't need the card anymore since I now have the business blue plus card with no annual fee. I would have kept it if she gave me a big credit because i would have used the airline credit again next year to make up the difference.