This follows the logic that if a tourbillon was created to be a chronometric device, then in order for it to be set accurately, it had to have a stop-seconds or hacking seconds function. Think about it this way. Back in the day when the SAS (Special Air Service) were using their 5517 MilSubs to coordinate clandestine attacks, they set their watches to the same time down to the second. Which was why it was important that their watches had a hacking function.
You couldn’t say to your commander, “Oh wait, hang on, sir, the seconds on my watch doesn’t hack, it keeps running. Can I be approximately synchronized with everyone else?” This would probably result in your being jettisoned from the cargo bay of the transport plane sans parachute. And you would deserve it, right?
So then, how is it that while there are hundreds of tourbillons in existence, there have only been six wristwatch tourbillons with a stop-seconds function? The answer is, they are difficult to make and a pain to set up perfectly. But once they have been set up, they are clearly superior to versions without stop seconds.
Even Breguet saw the technical merit in the creating of a stop-seconds tourbillon as he made at least one example of this watch during his lifetime. This was No. 1176, the Garde Temps Four-Minute Tourbillon, dated to 1809. The first wristwatch tourbillon with a stop-seconds function dates to 2008 and was the A. Lange & Sohne Cabaret Tourbillon. This watch was discontinued in 2013 but it has been revived this year in a stunning Handwerkskunst limited edition.
Lange’s innovation was to create a Y-shaped stop-lever to stop the balance wheel, even when one arm was potentially blocked by the pillar of the cage. This same solution was used for the 1815 Tourbillon, which ingeniously incorporates a heart-cam on the tourbillon pinion to make for a zero-reset seconds hand when the tourbillon is arrested.