The first U-Turn ramp is there because right now they are building an overpass right over it so basically it will have an exit in which you will be able to do a U-Turn under the overpass, and then get back on Loop 20 West and go North or South on I-35.
I knew there was something about this interchange I couldn't put my finger on. Seemed to be a little more open and "bigger" than normal, even for Texas.