I read Ord's report and don't understand your point. Sometime after 4 pm, Grant tells Ord that Rosecrans is too far from being in position for Ord to initiate the battle. Grant then tells Ord to move up within 4 miles of Iuka. Ords troops have been 6 1/2 to 7 miles out and skirmishing with the confederates. Ord issues orders to move up within 4 miles. He receives Ross' message about 6:00, who says the confederates are evacuating and burning stores. Ords troops finish moving up at some point after this.
It's basically that Ord stuck to the letter of his orders to not attack until he heard the sound of gunfire, even though he'd had evidence that
something was going on before 4PM and his orders to advance were given to him around 4:30 PM (per Cozzens at least). What Ord could have done, for example, is:
1) To follow up by launching a recce supported by artillery fire at sunrise on the next day, because:
- If the smoke column was Rosecrans, then Rosecrans is close enough that this would indicate he could resume engagement.
- If the smoke column was burning stores, but Rosecrans is close enough to attack that morning (which should have been obvious from the dispatch by Rosecrans about having been in a fight the previous evening, or could have been inferred from Rosecrans predicting his arrival at 1PM to 2PM on the 18th) then it would bring on an engagement from both directions as the plan outlined.
- If the smoke column was burning stores and Rosecrans was too distant to get involved that morning, then the plan is in the process of failing as the Confederates are abandoning Iuka. In that case an attack on their rearguard might be preferable to letting them get away unfought.
2) To follow Grant's orders to attack early on the 19th.
Simple enough.
3) To have Ross ready to move promptly when ordered, and to send those orders shortly after Grant told him to move up, thus getting Ross moved up much earlier than actually happened.
Grant's HQ was at Burnsville, and Burnsville is 8.2 road miles from Iuka. With Ross 7 road miles from Iuka this means that Ross was barely any distance away at all; it's actually kind of astonishing that the dispatch from Ross is supposed to have taken two hours to reach Ord.
Given how fast Rosecrans moved that day (it looks like ~18 miles in 10 hours), Ord's movements come across as slow by comparison even given his start time.
This doesn't mean Ord acted wrongly on the 18th, necessarily, it means Ord didn't showcase any particular aggression, or rather that we cannot use this incident to argue that Ord showed a willingness to act aggressively.