One of my friends studied at CSVTU. According to him, there are various kinds of people who check answer sheets.
It might be a new M.Tech graduate student. An experienced professor, who could have 20–30 years of experience in education. So, definitely, you can predict the difference in marks for the same answer sheet. And, that is the reason why similar answer sheets of students get good marks while others don’t.
This is different in this case. In backlog exams, they get time to read your answers properly because of less number of sheets to check. That sometimes is checked strictly. Thus checking papers could sometimes be done lightly or sometimes harshly.