If he's an engineering, science or whatever from BYU, it's not so important. However, even if you want to go to BYU, prepare well for the GMAT. The GMAT may be more important for you at BYU than at many other institutions. At BYU, you are not unique (regionally, ethnically, mission, etc.) whereas at Indiana (for example) these are diversifying qualities that get you some points in the admissions process.