The author's foreshadowing creates suspense and that takes forethought. Your story structure may be weak or non-existent. The plot may only be regurgitated movies you've already seen. It may be hard to rewrite. It becomes harder to cut out scenes you love.
Writers try to jam in past written scenes that have no relevance in the new draft.
This approach could take longer to get the script where you want. The story will be missing a lot of elements and you might want to trash the entire draft. If anything is salvageable maybe you can create your next draft around the most fascinating sequence. Using this approach This approach is good for writers without much patience and who have been brewing a story in their head for a long time. As you pour out the words onto the page keep your characters' objectives in mind.