I heard him discuss the topic with a small group of fans at the end of a signing, as he was rewriting Way of Kings.

Someone asked about Hoid, and Sanderson embarked on this explanation that he had this kind of personal game, that he's always loved to put limits and rules on his writing before even beginning to envision the story development (he's far more comfortable and stimulated by that than by open systems he later bends to fit a developping plot, he said doing that was very important for some writers but for him it made him fall into lazy storytelling habits) and that he had this kind of meta-system he's created very early on, a kind of larger cosmology he's challenged himself to include in most of his novels. That cosmology has some rules he forces himself not to break when worldbuilding for a new setting. He gave the impression that for the most part the more overt signs of this in the books were for the more "geeky fans" who like himself like this sort of things, and that he expected the more casual readers to totally overlook this and it was fine. He did say however, that in some of his series like the Stormlight Archives he was likely to include more elements from the "meta system" as the story demanded it. He didn't give the impression of someone who had a big masterplan to gradually unveil the cosmology through multiple series, he really rather sounds like he was having fun with the constraint he put on himself with this element the average readers are not terribly conscious of.