That's odd. Johnny Cakes are such a Rhode Island thing. I was born there. In the south nobody has heard of them.
Probably different names for the same thing. Johnny Cakes sounds a lot like what we call fried cornbread or some call Hoe Cakes. I don't know if they are the same or just similar. We often ate fried cornbread as part of our supper like some folks eat rolls or cornbread with their meals.