It means that if there isn't a trial then no one has to testify in a public forum, both clients and prostitutes. So the innocent don't get hurt.
Also I doubt the police or prosecutors are going to do anything with client lists as they've gotten the result they are looking for. They have anything to gain by making those lists public. In fact, if they want to use the list for possible future interviews to gain further info about other agencies, ladies etc you'd think they would ewant to keep it secret. The only leverage they have to get information is the threat of exposure. Once that's gone, poof.