I think Jerry wanted to have the Rangers ballpark in view out of one end of the stadium, which it is aligned out of the east (non-sun end).
Also, I think their plans were that an office/hotel would eventually be part of the development at the west end and would be used to eventually block the sun. I don't know if that holds water at all (probably not), but I've heard it used as an excuse. There is at least some space there for that potential.
Here's a parking map where you can see how the east end of AT&T pointed at the Rangers ballpark in green. You can also see that there would easily be room for a hotel or office building at the corner of North Collins and Legends Way at the west end of the stadium.