But this was my point. We can't always rely on rules and limitations that are established later in the series. If we did, we'd have to assume that Rand was channeling the True Power when he Traveled at the end of TEOTW. For that reason, Shai'tan's constraints when "snatching" souls doesn't necessarily mean that he didn't have the ability, back when Jordan wrote TEOTW, to grab and torment Kari's soul.

For all we know, Shai'tan started out as a something of a God of Death or the Underworld, who had total power over the grave and the dead, and grew into an Enemy Outsider God.

But it's a fairly academic argument, because the best explanation is that Rand subconsciously summoned Kari, so it doesn't matter if the Dark One originally had the power to grab souls willy-nilly or not.