Our courses are to model real life and in real life, deadlines are often missed. But to master swimming, we have to jump into the water without this skill, and the same relates to deadlines. We think the experience of facing and coping with the deadline is extremely valuable.
And it shouldn't be theorized — you better make a common decision with your team in the circumstances that happened, should you cut the scope or prolong the duration, etc.
From our side, you still will have access to everything after a deadline, so that you can finish the project anyway.