This confirms what we've expected since DX12 was announced -- the API may offer performance improvements in certain scenarios, but DX12 isn't a panacea for the Xbox One's lackluster performance compared to the PS4. It's an API that appears to mostly address scenarios where the CPU isn't able to keep the GPU fed due to draw call bottlenecks. In other words, Mantle and DirectX 12 are slated to perform best when a CPU can't keep a GPU fed. And that can be a problem -- but it isn't an automatic problem in every title or scenario.
It's entirely possible that the custom, Win8-derived OS that MS already runs on the Xbox One has less problems in this area to start with. Failing that, draw calls simply may not be much of a problem for the Xbox One overall. In fact, were we to suspect a problem, it comes down to other aspects of the system design -- either the 10% of hardware that's still reserved for Kinect, possible utilization differences between Sony and Microsoft's OS environments, or the size and speed of the 32MB onboard EDRAM cache.
The long-term benefit of DirectX 12 is that it may give developers the option of taking advantage of multi-threaded CPU cores in a way they currently can't -- but since those benefits are blocked off in DX11, simply porting a game to DX12 isn't enough to unlock its potential.
The big-picture good news out of data is that performance updates and possibly a resolution boost for Titanfall are still coming and gamers won't have to wait until 2015 for a DX12 release to take advantage of them.