That's not really true.
Jordan had written EXTENSIVE notes on exactly how pretty much every major plot thread was to be resolved.
George RR Martin has done no such thing, and actively avoids telling anybody concrete information.
It SEEMS to be that he gave the showrunners a roadmap to finish the TV series roughly equivalent to how he wanted to end the books, but given the insane backlash to how poorly they execute it, I think its highly likely the ending of the books will change (if we ever even get it).