Benton Park has many of these enfant mansards, especially along Lemp Street. I don't know why they're only 2/3 the size of a regular 2nd Empire. I've heard that the small stature permitted the homeowner to show off a mansard roof line without the expense of a larger house.
These and Lustron homes are my "isn't that a cute little house? I'd like the pluck that up and put it in my pocket!" I ordinarily like houses that are the architectural equivalent of the nickname assigned to my husband by his college friends: the Big American Giant.