The mechanism

Payment and release are two halves of one event. A half-finished sale is not a state this can be in.

Both legs, or neither

Payment moves to the seller

Release moves to the buyer

Both, at the same instant One without the other is not a state this can be in

Not an escrow holding funds in the middle, but a settlement where a half-completed outcome does not exist to be argued about.

The buyer commits the payment and the seller commits the release. Neither has parted with anything yet.

Both legs execute together. There is no ordering to argue about because there is no ordering.

If either side does not commit, the arrangement expires and both are exactly where they started.

Nobody takes custody in between. That is the difference between this and every escrow, and it is the whole reason to build it this way.

Payment and release are two halves of one event. A half-finished sale is not a state this can be in.

Neither First does not