Its hard to say if the UHD player would be, or not, a good move.
Lets compare this with some other stuff: the iPhone.
Every two years we get a new iPhone, and after that we get a revamped version, the S!
The S is a better and faster machine, but keeps its roots on its original.
For instance the iPhone 6 and 6 S major hardware diferences are a faster APU and a better câmera.
You could give him bigger hardware changes, but if the similarities to the model that gives him the name, the 6, are too big, it would be better to call it the iPhone 7.
Although I think the Xbox One S did the right moves when including the UHD drive, I also think Microsoft did something that not all Xbox Fans liked. It gave then capabilities the original console does not posess. Not just improvements, but brand new capabilities. But this was a must to improve sales, specially against a rummoured more powerfull PS4.
And this is where I think Sony stopped. Because the PS4 was already a best seller. The PS4 was designed to do what the PS4 does, but only better. But not to do things the PS4 cannot do. It does improved gfx and improved resolution, but on the exact same games that run on PS4. All software, peripherals, and all kinds of media supported by the Pro are exactly the same as on the PS4
Under this perspective, adding the UHD player was a bit too much.