The Cal 956 housed in the TT DSA is the same than the one you will find in the TT Polaris and the 2010 Master Memovox.
The only difference being the date ( which has been removed in the TT DSA ) and the alarm sound.
Why?
Easy. On the TT DSA, the JLC team involved in the development of this project wanted to have a faithful approach, and not only aestheitcally, but also acoustically.
So, this choice was motivated by this reason: To be the closer possible to the original, nothing less, nothing more.
And this is an official answer.
Best,
Nicolas