The caliber 74, like many other movements, is based on an AS 1687/8 ebauche.
Because of this, there are often "empty holes" in base calibers where the particular location isn't used in the adoptive caliber.
The Cal 74 auto design was developed by a consortium (Zodiac, Doxa, Girrard Perregaux and others) so if you look at some of their calibers you'll see the same empty holes.