And the French had locked one army into Metz and allowed another to be encircled, outnumbered, out of supply, and essentially smashed trying to break out; in some ways, it is quite analogous to the rebels at Appomattox.
And since we're talking about the rebels and the US, that's what was meant, not the larger scale of Nineteenth Century conflict, but it holds equally true...
None of which was going to apply at Shiloh, since obviously, the US forces were not encircled, outnumbered, out of supply, and in a position where they'd have to attack to break out.
Best,
My point is it was possible, when as you put it, "movement and maneuver is based on the pace a marching man carrying his weapon and ammunition and rations could sustain" to obtain an annihilating victory. The attackers were not always slower than the defenders. Your example of Appomattox is another case in point.