It does not matter really unless the mint punishes the sender for double-spending afterwards but imagine:

Alice has a million bucks with a mint, represented as Chaumian tokens. She now clones her device and walks into the desert to meet Bob. Bob shares his public key with Alice. Alice signs the million bucks over to Bob's pubkey.

Now if Alice destroys her device and uses her pre-transaction-clone of it, to send the funds to a different receiver before Bob could talk to the mint, what magic other than later punishment for a provable double-spend could there be to prevent this claw-back?