It's not just negating a case in chief point.
It's on the heels of the defense negating in pattern form the foundation of a large deal of the pros case in chief in an untimely manner that may take more time than allowed to in this case. The cross and rebuttal of the evidence may be pointlessly prejudicial and not as probative as it seems from first glance.
That was part of the appellate ruling I quoted. It does not matter if the new evidence does not directly negate a case-in-chief point or does more than just negate a point.
The defense witness said "that router is big".
That was not said just to entertain the jury.
That was part of a new theory offered by the defense.
Something like: "no one found an fxo capable router in the house, and they are big. Someone would have seen one if there was one there."
The prosecution is allowed to enter new evidence that rebuts the new theory offered by defense, even if the theory was offered only by inference.