Massachusetts Vital Records - Father's surname

I am doing my first review and it is birth records, specifically Massachusetts Vital Records. The record lists the child's given and surnames, the father's given name, and mother's given and maiden names. There is an entry field for father's surname. The indexer sometimes put "blank" and sometimes put the child's surname. I believe the general instructions say not to infer surname's based on other family members. Do I change all of the father's surnames to blank?