So looks like AMD made a mountain out of a molehill?
http://wccftech.com/amd-launches-mantle-beta-low-end-cpus-not-gpus/
A 290x with a top end Intel CPU sees BF4 performance increase a maximum of 10%?
With a 260x the increase is of just 1.4%!
The larger improvements are for AMD CPUs and even then only 17.3% at the highest settings.
And then they showcase Star Swarm Demo to make a point, hiding the fact that this engine was built from the ground up to do precisely that. Mantle only came after.
It looks like they are just launching this now, to save face. They even say its Beta version.
Did you read the BF4 patch link with Dice's own tests?
http://battlelog.battlefield.com/bf4/news/view/bf4-mantle-live/last/Multiplayer = 7970 + 8350 = 25% faster
Singleplayer = 2x 290X + i7-3970x = 55% faster