No idea what this guy is talking about. Big tech are only talking about the existential risks to hide talking about the actual very real risks of how the technology will be misused.
IMO the biggest risk is that big tech will be the only ones allowed to do AI in a future regulatory regime, leaving smaller players out of the wealth making opportunity, and leaving society with a low diversity of options. And that regulatory capture is enabled ironically by people like Tegmark, who are pushing for restricting everyone with bureaucratic nightmares.