I gotcha. That's an interesting point. Normally AA flights do allow holds, so that doesn't require a refund. Since the system doesn't allow holds with an eVoucher or GC, these should be subject to the 24 hour refund rule.
The internal policy states that any reservation that cannot be held on aa.com is subject to a refund. However, it does not spell out the list of exceptions, such as reservations that used promo codes.
Note, though, that even if they grant the refund, the value of the eVoucher is gone and can't be used again, so this would not be a good plan.
As gemac notes, these things can't be applied to held reservations (AFAIK). What likely happened is that the agent just recreated the same itinerary since inventory was available, and didn't apply it to the hold. At least that's my understanding.
eVouchers work like gift cards. They come with a pin number and such. So it is possible to get those refunded, but it certainly won't happen instantaneously.
Since they work like gift cards, you can apply them to held reservations,