I don't get where you are getting your numbers from for the 7850, but I suspect it's a case of the 950 being 4 years newer and being optimized for the games used in the review.
A fairer comparison is the Radeon r7 370, which is the same silicon as the 7850, but obviously released more recently (and hence reviews have been done with more contemporary drivers.
http://www.guru3d.com/articles-pages/msi-radeon-r7-370-gaming-2g-review,16.html
Good example of a review of the 370, and shows its equal to the 950 on average. I bring this up because it totally changes your analysis. You go from Maxwell being 30% more efficient to 0% from a fps/flop perspective, and really goes to show that flops is a really dumb measure of performance. It is a measure of compute, but fps is more than just how fast you can calculate shader ops.