It’s just a style of house. Raised Ranch. Front door opens to a set of stairs. Down is the first floor up is the second floor. Usually the main kitchen living and bedroons are upstairs and then downstairs was usually a recreation room, spare bedrooms and maybe garage.

Since the pipes were going up to the second floor kitchen anyways it made sense to make an added kitchen downstairs under the main kitchen for an in-law or secondary kitchen if you’re entertaining downstairs.