Actually I was waiting for someone to bring this up, thanks Demandred. If you go back and read both encounters, you will realize that Ishamael meets Rand in the Dreamworld, but Ishy is not there in the flesh. So when Rand cuts him off from the TP there it does not extend to the real world. Just as when anyone is cut off. But you will notice a different reaction to when he is cut off in TDR. Since it occurred in the flesh, both sides of the Black Cord rebounded and for a second Rand saw a blurred vision of Ishy two in one kind of view like what he saw when he cut Asmodean off. This did not occur in book 1 for the reason I just stated. But I do understand your confustion :)