The reason that Texas is not full-court pressing Aaron Green is beacuse the Longhorns are pretty deep and young at RB and they would prefer to only bring in one more RB in this class. They must either feel they have a better overall chance at landing Malcolm Brown than Aaron Green, or they simply prefer Brown to Green. Heck, they may be going harder after Brown because they feel Green is a Husker lean?
The point is that their class only has 2 or 3 spots left and when you are a school like Texas and you are capable of recruiting anyone, anywhere, you have the luxery of spending the majority of your time trying to secure a commitment from someone at a more desired position. They can play hardball with kids because they know that they can replace a 5* or 4* player who says 'No' with a fellow 5* or 4* player. Most schools outside of Florida, USC (until recently), Alabama and a select few others can pull this off. Texas can.