I disagree... I think Brandon Sanderson is handling everything correctly. This isn't BS's story it's RJ's. This isn't a broken down series that is crawling towards the finish line, even though some fans may think that. This is a series that is making a habit of debuting at #1.
A lot of people only know BS from the Gathering Storm, and have never read any of his own work. If he starts giving himself too much credit it may be viewed as taking credit for the series or being disrespectful towards RJ. That would inevitably turn away many potential readers, not to mention take attention away from the story.
Of course I don't think that book sales is the main reason why he's handling all the praise the way he has. He appears to be a genuinely humble person who knows that he wouldn't be getting all this praise for tGS if not for all the notes and outlines that RJ left behind. I also think he's respectful and appreciative for the opportunity that has been given to him. Everyone knows he did a great job on this book, but when everyone is patting him on the back for a job well done is it necessary for him to pat himself on the back too? I don't think so, and I think it's very classy of him to redirect praise back to Robert Jordan.
If the tables were turned and Brandon Sanderson was the one who left the notes behind for someone to finish a series of his, how would you want that unknown author to act? If that book then debuted at #1, how would you want that previously unknown author to act? Personally, I would want that author to show the same humility and respect towards BS, as BS is showing towards Robert Jordan.
Of course, just because he's not acting like an athlete talking about his SportsCenter highlight doesn't mean that he doesn't realize he did a great job. In his previous blog post he didn't say that, "I hope Robert Jordan is smiling", or that "Robert Jordan might be smiling", no what he wrote was, "Robert Jordan IS smiling."