The voice isn’t his to own in the first place. “They” have a right to use it as much as he does.
No, it's fraud. The CEO of the other company admitted that they consider this to be infringement, and it was done to make the video more popular, which to me means the staff did it so people would assume Jeff Geerling supported the video (and there's evidence that viewers did initially make that assumption).
So it seems clear to me that Jeff Geerling, Jeff's viewers, and the CEO of the company producing the videos with the voice imitation consider it to be infringement, and I believe it amounts to fraud.