Wasl is a connected utterance whose parts are read together; fasl is a separation after which the first statement stands independently.
Lakin has different consequences depending on this distinction. In connected speech, the denial and affirmation may qualify a common subject. After a legally effective admission has been completed, later words may amount to a new statement rather than a permissible correction.
The issue is not a mere pause in pronunciation; it is whether the initial statement was complete and legally operative.