That would provide no protection against being disappeared, and potentially make things more dangerous for people in that situation.

Assume police do disappear people. Opting for your record to be public would show police that you're willing to cause problems for them, making the prospect of getting rid of you more appealing. Further, if some associate of yours goes to find out what has happened to you, they can just lie and say you opted for a private record and send the person away.