It's a bit similar to the test-optional trend in undergraduate admissions. The acceptance count (numerator) generally remains constant, while the application count (denominator) increases as more students see the appeal of omitted test scores. So, the acceptance rate decreases, which can craft a façade of prestige, among other things. Additionally, that increased applicant pool may include some higher-achieving students, likely applying for safety purposes, which can increase prestige if they accept; furthermore, their acceptance pushes otherwise-capable students to a lower priority in the pool.

All in all, in order to effectively analyze these occurrences (particularly in admissions), one must ask: how will the institution benefit? They wouldn't pass these changes otherwise.