Former PSA student here. The PSA schools offered are not based on the major but on meeting admission qualifications at the PSA school. For instance, one of my friends was offered just one PSA school (West Texas A&M). I qualified for all eight PSA campuses and chose Corpus Christi. Here are questions/answers from TAMU’s PSA page:
Why can’t I see all eight system schools on AIS?
Each system school has provided minimum academic qualifications to guarantee admission. Some students may qualify for admission to all system schools while others may qualify for only one.
What if the system school doesn’t have my intended major?
The major choice at the system school does not matter. System schools who do not offer your intended major will place you in General Studies to allow you the opportunity to take the required coursework for PSA.