I don't think we disagree. One way of evaluating it was to think that Hooker's divisions would remain closer to Bridgeport and possibly ferry an engine or two across and reduce their logistical load that way. If Sherman was moving, he would probably come in from the west and meet up with Hooker from that direction. That involves some wishful thinking about Thomas being forced to attempt a withdrawal, as had occurred at Chickamauga.What Longstreet thought is thoroughly documented. He dismissed the threat of any attack to secure a bridgehead at Browns Ferry. As we know, two A of the P Corps popping up like a Jack in the box never entered into his planning. The documented record on that subject is unambiguous.
They weren't thinking about Thomas and Smith eliminating the north bank route almost completely and the little steamers being brought into operation and the river being cleared of all practical artillery fire. They had not really comprehended what Grant had planned at Vicksburg. The correct concept of Civil War logistics was to use the most water born logistics as possible, and as few wagons and mules as possible.
Longstreet was thinking conventionally, as if he was dealing with one of the eastern generals. The triple convergence was an audacious plan, involving close cooperation between three forces and an amphibious attack. Its not hard to understand how shocked the Confederates would be when the saw the US forces had no intention of retreating.