If one party fails to move forward on the transaction according to the committed schedule, that party is penalized and the counterparty shares in the reward. But if both parties consent, the transaction can be unwound fully without delay. Cryptographic protocols put in place as part of the lock-in step are able to handle each potential case and can be mathematically proven correct.

(Without property 4: The assets of one party can be tied up for an extended time by the other party, not only discrediting the system but inconveniencing the users and even subjecting users to potential extortion.)