“Untraceable” is a strong promise and I'd be surprised if traffic analysis couldn't de-anonymize effectively with the investigatory resources which a nation-state can muster.

The other key thing is that Bitcoin fails open: if anyone anywhere ever makes a mistake or is subverted the blockchain is a public record of every transaction which is hard to deny and can never be purged. I'm not sure anyone has the operational competency to make assurances in that environment.