The dilution rationale behind the supposed exclusion makes no sense, either. Alabama, Tennessee, and Mississippi have multiple SEC teams (and are much smaller states than Texas) and no one worries about brand dilution there.
Point very well taken with UT being hard to work with, though. The SWAC might still be a thing were it not for UT getting greedy and being hard to work with - and A&M would certainly still be in the Big XII if UT was better behaved.