Typically it means that you have been undercover, such as a secret agent or police agent, and you are now letting everyone know that you were really undercover the whole time. It’s called “breaking your cover”.
For example, if I have been working undercover as a police officer in a drug bust, and the big day where we are going to apprehend everybody finally happens… At the moment of the arrest, I might break my cover by screaming “police, nobody move, hands where I can see them! ”
As far as what it means for a USB-C cable, I have no idea.