This was back in the 60’s and the family had just moved from SC up to MI.
I don’t think they thought much of it, seems where they moved from there was no such thing as building codes out in the country. The house was approved, they had a building permit but I don’t think they ever submitted a site-plan.
Back then perhaps that wasn’t needed like today.
Site plan is part of the package you give the building inspector. I added a garage to my property, and we were well within the set back (which was like 25 feet), maybe a good ten feet to spare. It was a 24’ x 24’ garage, attached via a 6’ foot breezeway, which would tell you it extended 30’ from the edge of the house. The building inspector wanted a survey, which would have cost over a $100 bucks, but I whined enough that he waived it. (Clearly it was compliant.)