The Yazoo River is just too small for large vessels.
That certainly could have made the "New Orleans" double-ender design useful... if you don't need to come about, that's an advantage in narrow places.
One thing to recall when discussing size is draft-- when you want to float a large amount of tonnage, you can either build down (increased draft) or out-- so long as you're displacing the same weight of water, it will float. For a shallow, narrow river, a large (but shallow) double-ender would seem to be well-suited for the conditions. (Though I would wonder if the resources wouldn't have been better-spent building two smaller vessels. Perhaps part of the calculation was the option to sink it in the river as an obstacle as a last resort.)