How to disclose parental name change on form DS-11

According to the current* DS-11 US Passport Application, on Page 2, under 10. Parental Information, the applicant is asked for the following two pieces of information about each parent:

• Mother/Father/Parent - First & Middle Name
• Last Name (at Parent's Birth)

Notably, the first field (First & Middle Name) does not have the "at Parent's Birth" qualification.

What names should be listed if the parent in question has legally changed their name? From a literal reading of the fields above, the form is asking for the current first and middle name of the parent but the birth last name. For example, if my father was born as John-Jacob Jingleheimer Schmidt but legally changed his name to Thor Hammerman Odinson before I was born, I would be expected to report his name on the form as Thor Hammerman Schmidt, but this seems absurd, as this would represent a name he has never used - his birth certificate presumably has John-Jacob Jingleheimer Schmidt, and my birth certificate would list my father as Thor Hammerman Odinson. Am I reading too much into the form, and they intended to imply that I should put down the entire name, first, middle, and last, as it was at the parent's birth?

*Note: I am aware that the document above has an OMB Expiration Date of August 31, 2019. Current guidance from the US Department of State is to continue using this form for the time being.

This question has nothing to do with how to falsify or get away with falsifying a US passport application. Rather, it is about how to honestly answer the questions at the required level of detail without inadvertently falsifying it or otherwise causing myself or the government a headache.