Here is the exact wording from the TMDSAS Guide:
After 5:00 p.m. CST on May 15, no medical school in Texas may offer a position to a Texas resident applicant already accepted by another medical school in Texas. This is the result of an agreement among Baylor College of Medicine, John Sealy School of Medicine at The University of Texas Medical Branch, Long School of Medicine at UT Health San Antonio, McGovern Medical School at UT Health Houston, Sam Houston State University College of Osteopathic Medicine, Texas A&M College of Medicine, Texas Tech University Health Sciences Center Paul L. Foster School of Medicine at El Paso, Texas Tech University Health Science Center School of Medicine at Lubbock, Tilman J. Fertitta Family College of Medicine, University of North Texas Health Science Center Texas College of Osteopathic Medicine, The University of Texas at Austin Dell Medical School, The University of Texas Rio Grande Valley School of Medicine, The University of Texas Southwestern Medical School, The University of Texas at Tyler Medical School.