The 4001086-3 cable is not included within the kit and your dealer needs to order this cable from Ag Leader.  It is separate because the cable out of the Seed clutch module is different for air vs. electric clutch.  Probably the dealer incidentally over looked this cable when he placed the order. 

I don't know about lead times on cables or when you can get it but I would have your dealer call asap and get it ordered so the cable can hopefully be there before you start planting.  You may want to layout the cables tomorrow along the planter to ensure you have enough lengths and don't need anything else pictured in the system layout.  Its better that you found it now with 2.5 weeks vs. needing it tomorrow.