I have changed front brake rotors and noticed two extra holes in the hub and in the brake rotor. The holes are matching with each other. The purpose of them are unclear for me.
The car: Astra H 2012 model year.
The brake rotor: ATE 24.0125-0131.1
Then I have searched for similar (with extra holes) brake rotor and hub examples and found enough, see pictures in the bottom of the question. There are the cases with non-matching hub/brake rotor holes - 9 in the brake rotor and only 5 in the hub...
The question: what is the point of this extra holes and why in one case them matches (my Astra H) and in another case them doesn't match (Volkswagen Golf, Skoda Octavia)?
The Astra H's hub
The Astra H's separate brake rotor
The Astra H's hub and the brake rotor assembled
The Astra H's brake rotor back side. It is not having drum inside, so it can't be used with brake shoes, thus, these holes can't be designed for hand brake adjustment.
Non matching holes examples:
The Skoda Octavia's hub and brake rotor
The Volkswagen Golf's brake rotor
The Volkswagen Golf's hub