I'm in the production/entertainment industry so deal with many of these issues on a detailed basis, but I've learned that there are many times when there isn't a contractual obligation to do something, but for the sake of maintaining a positive relationship for future projects, an estate holder is sought out to make sure they have no issues with it. Even if they COULD publish these novels, perhaps they feel that doing so without Harriet's expression permission would cause more problems among the WoT fanbase than was acceptable. There is the possiblity, for example, that Harriet might refuse her permission at a certain point in time, and then reverse her decision in the future for her own private reasons.

Simply put, we don't have access to the contracts and agreements in place between the Rigney Estate and Tor's publishing entity, so we really can't read into the specific details of a public statement. What I've learned from my experiences is to let the signed agreement do the talking and not really put as much weight into public statements. After all, the details of the contracts are sealed by attorney/client privilege, and unless you approached them with an offer, there would be no reason for them to be told of rights limitations. Basically, we don't know the extent of the rights still owned by the Estate and the rights owned by Tor - it's quite possible that Tor owns the rights to the earlier stories, which would make sense given their re-releases, while Harriet owns the rights to the story, the characters, and etc, with those rights being given to Tor in a series of limited buyouts. It would take a more detailed legal analysis to really get into the state of the rights IMHO.