I would say that makes it further unlikely that we will get a Graendal PoV from before her death in ToM, as some people like to suggest (e.g. Graendal chatting with Aran'gar about something), because it's stuff that could have been in TGS and apparently BS wants to avoid this.

I also found the following statements from BS in his Mistborn annotations, which IMO further support that it's unlikely that BS would basically jump back in Graendal's plotline:

"I like to avoid flashbacks when I can - they're usually more of a hassle and an annoyance than they are useful."

"I generally follow a straight chronology in my books — meaning that page 22 is almost always later in time than page 21, no matter which characters happen to be on the different pages."

Of course, BS has to jump back in the overall timeline to those characters in ToM, who are behind Rand and Egwene at the end of TGS. But considering what BS says above, it seems most unlikely that he would do something - also RJ never did - namely giving a character, who died in his/her timeline, a PoV from before the death in the next book, especially if other characters could simply reveal more about Graendal as well, if it is necessary (like BS said, Graendal's name will be mentioned a few times in ToM).