Front-and-center is not the way I would describe it. They're squashed to the left, leaving huge swaths of empty.
Notice how the actual functional buttons in the banner are tiny, have no frame around it and no hint that they're clickable. They're tucked away in a corner and almost an afterthought. Also, definitely not touch-friendly. (I suppose that paradigm is dead now.) Looking closer, I especially like how there is an 'additional functions' button at the end even though there's plenty of space to put more buttons.
Most of the space is just wasted on a pointless gaussian blur that would get old real fast.
Also note how the actual functionality (in the article picture for groove) is to display icon lists of albums, and there are certainly more than can be fit on the screen. The humongous banner comes at the cost of reduced functionality.
>As a design tool it's neither good nor bad, user hostile nor user friendly
The way tools are implemented and marketed can either push third-party devs towards user friendliness, or away from it, e.g. by making certain choices easier/harder or by promoting certain reference designs. The message I'm seeing so far is definitely not towards encouraging user-friendly UI.