Why would it break ? Since it's only applying the back brakes via a cable rather than the hydraulics I would have thought you would just come to a stop,..eventually
I would agree that it's not something to try unless it's an emergency or as an academic exercise on a track
I had this done to me when I was driving at 50 mph. My passenger thought it would be funny to blip the hand brake on. Unfortunately the ratchet engaged. The back end just waved around as if on ice. Despite me trying to keep it straight we eventually came off the road into a ditch. Needless to say I don't see that friend anymore,
The obvious use for the handbrake is to prevent vehicle movement when parked but it is tested on a rolling road in the MOT test and the examiner can see whether the effect is the same on both of the wheels (on the 2cv by the way the handbrake works on the front wheels not the back ones - just to be different!). Provided you keep the ratchet off it can be used as an emergency brake but don't make a habit of doing it! Back to the 2cv again these cars have a warning light for low brake fluid as well as a press button to check that the warning light is functioning.