Dutch doors originated in colonial New England. Divided horizontally so that the top and bottom portion of the portal can be opened independently, the Dutch door was practical solution that allowed for open airflow while still providing a barrier to keep children in. Dutch doors are also know as half door, split door, stable door, or double-hung doors. They were a prominent feature in Dutch Colonial homes, so the association with the Dutch stuck.
We find that Dutch doors can also serve a good purpose for chicken coops. You can throw table scraps inside without letting the birds out or prevent some dogs from getting in the run.
One thing for sure, it looks amazing.