Dear etaoin: I can't find any documentation, but I suspect very strongly that cooking drives out any of the additional flavoring agents in natural vanilla, so that the extra money is wasted.
And in Chinese food, I think celery is a very welcome addition.
I still doubt very much that any of you soi-disant gourmets have ever seen blanched celery (no chlorophyll in the stalks because of the hilling up to shield stalks from sunlight). I did see some celery roots (not on the stalks)
in a supermarket in VA maybe eight years ago, but no blanched celery.It's apparently the chlorophyll that gives celery the bitter taste.