Tiling is not "Microsoft shitting rainbows". Tiling in fast RAM has been something used on AMD GPUs including the Xbox 360 and in all the Adreno mobile GPUs. This tiling does add some overhead though.
The memory bandwidth is only half of the story though. A bigger problem is that by having eSRAM taking up area on the die, the XB1 had to cut Compute Units. The XB1 has 12 CUs compared to the PS4's 18 CUs. There are also other units reduced, like texture units and frame buffer units. Those are the units that do the actual shading, texturing, and writing of pixels.
When going from 900p to 1080p there are 40% more pixels to shade, texture and write, and there is no way to "shit rainbows" and make up for those missing CUs and other units.
