All the places I've interviewed for, you talked either to the person who was going to be your boss (or teamlead or whatever the word is), or at least someone who would be a direct colleague on a daily basis. If a sibling or cousin could do my voice and mannerisms reasonably (as well as the job I want to get), perhaps that could pass, but otherwise I don't really see this happening.

Hm. Unless the employees don't want to ask because it would be so awkward if they're wrong about the candidate being a different person from who shows up for the job?