The mobile versions of the desktop GPU's frequently fall well below the desktop TDP. A desktop 950 vs a laptop 950 are *not* the same by any means. Not a perfect example, but people keep referencing desktop cards and asking for them in a laptop, and even still with same name does not equal the same product.
http://gpuboss.com/gpus/GeForce-GTX-950M-vs-GeForce-GTX-950
http://gpuboss.com/gpus/GeForce-GTX-950M-vs-GeForce-GTX-950