If we put back Palpatine’s line, “I never wanted you dead, I wanted you here,” it would not be clear that he changed his plans. Originally he really did want her alive all along, even when she was a child. The narrative for Ascendant is that he really was trying to have her killed, since he had already invested years and years into Kylo Ren with that mighty Skywalker blood. But when he was redeemed into Ben again, Palpatine made Rey the next target to corrupt and become able to possess. So if that line were reinstated, the audience would take it as the truth and be confused. And since we can’t have that line, the way to clarify he’s changed his plans is to interject something into the hologram scene. Unless we want “the Princess of Alderaan has disrupted my plan but her foolish act will be in vain” to do the heavy lifting. But it still wouldn’t help the audience see through Palpatine stating he always wanted Rey there.