Get a panicky call from "me" in the middle of the night? If I don't include my safe word, that call isn't from me.
It's not very important that the voice is similar to the supposed victim. Usually the person in the call is weeping and it's very difficult to recognize the voice. Moreover a confusing voice at 2am may be interpreted as any of your relatives or friends, but an exact voice can be interpreted only as one and it's easier to know that that person is safe.
He was 90% convinced that it was true, but my mother made him call me before doing anything, which saved him about $10k. She thought it was suspicious that I would have left the country without mentioning it to her.
If the person he was talking to was relatively calm and sounded like me, it might have been successful.
> Bububu. Hi, I'm ... bububu
> John?
> Bububu. Yes, I'm John. bububu. I'm in bububu ... the jail in ... bububu
> Mexico?
> Bububu. Yes, In Mexico. bububu. And I need money ... bububu
There are other that research the victim and have more data for a targeted call, but it's more difficult so most cases where random calls where they don't have a sample voice of the victim.