No. These plans make no assumptions about time, other than the ever present reality of crisis action planning that you will never have enough time. Time available is a critical part of determining operational or tactical feasibility when you pull a plan off the shelf and turn it into an operation. I do not know first hand, but I suspect that part of the job of the the additional forces is to buy time to accomplish the evacuation. The Taliban know full well that taking on U.S. soldiers and Marines in a prepared defense is a no-win proposition. They’ll pester them, cause casualties if they can, but they’re not stupid enough to play to our strength and fight a set piece battle.
Any plan is only a reference, as the proverb states, they never survive contact with the enemy. But it is the planning that already occurred, the information gathered and requirements identified that are priceless to those executing an operation in a crisis.