3 position 1911 hammer


I have a new S&W 1911 mil spec. I noticed there are 3 positions on the hammer. Full cock, half cock, and a very short cock. (no jokes please). The shortest cock seems to be usable for dry fire, unloaded of course. What is the purpose of this first/shortest position? I don't recall having it on other 1911's
Article discusses half-****, but not the third position.
You have a “safety” stop about 1/4 inch from the cock position, then half cock and full cock. It is my understanding that all do not have this “feature”. My Springfield RO did have it. The safety catch is designed if you were to slip your hammer it will not fire. I have read that some carry half cock.