"Impersonation of a voice, or similarly distinctive feature, must be granted permission by the original artist for a public impersonation, even for copyrighted materials."
Having someone sing in the exact same style as another singer is totally different from what OpenAI did with their voice AI (having a female actor speak in a flirty tone).
It makes sense with music but you're setting a really dangerous precedent if you can't even hire a voice actor who sounds similar for speaking.
Basically your voice is part of your likeness.
"Impersonation of a voice, or similarly distinctive feature, must be granted permission by the original artist for a public impersonation, even for copyrighted materials."