The video mentions that the audio was recorded separately, and shows a few other options like text-to-speech (which obviously doesn't match the voice) and some

The video mentions that the audio was recorded separately, and shows a few other options like text-to-speech (which obviously doesn't match the voice) and some smarter voice matching audio generation (VoCo) which could pass for the original voice sent over heavily compressed, low-bandwidth video conferencing or something like that. I'm guessing that if this is used for actual disinformation, finding a voice actor/audio engineer to try and match the speech would be most effective.