Well, the goal is crystal clear: They are turning xbox into dedicated windows 10 devices, but every win10 device plugged into a Tv will become an xbox.
With that in mind, it makes sense that they will push that every xbox game going forward will be play anywhere, but if they really want to make a splash they need to do just like what they are doing with 360 BC, acknowledge the purchases their users made and bring everything together under the same platform.
Bold prediction: Until the year's end we will see more of that, more titles supporting play anywhere and PC only games making into the xbox (Like Age of Empires II HD), with more unification each year, and until the end of xbone life we will have all their games playable through the store.