> indicating her voice was protected against unauthorized use
But it wasn't her voice, it was the voice of the impersonator. By that logic, the impersonator can never speak without authorization because the impersonator would use Bette Midler's voice.
>>rootlo+(OP)
They wanted people to either think that is was Bette Midler, or someone that sounded very like her to gain the benefit of association with her. They wanted to use some of Bette's cultural cachet, without her permission.