I thought the 12.9 had a Tru Tone display already?
Don't remember exactly, but I do know there's a bit of fragmentation between the 9.7" & 12" iPad Pros where each has a few features the other doesn't. Kinda annoying. As I've said before, I wish the only differences between the iPads, or between the iPhones was just the screen size. Don't add additional features to the big one in order to upsell, and definitely don't mix and match features. For me, having the only difference be the screen size makes sense. Keeps the product line clean and simple.