They could have easily made test scores a pass/fail per program and not weight higher scores for admission purposes. It achieves the goal of ensuring students have requisite knowledge for the program while not favoring students who are able to ace the test.
Or, even better - just expand programs so they can accept more students who pass the test. This would probably improve diversity without artificially restricting access to highish performers.
To expand the UC system to accommodate everyone who could do the work would require repealing Prop 13, much harder.