Its interesting that pixel shader is zero on the high word, and the order doesn't seem to follow a logical pattern. I wonder how they chose the order???
Seems evident enough. The first two shader stages that were available in the earliest hardware - ps and vs - are 0 and 1 (although I would have expected vs to be 0 and ps 1, but maybe there are historical reasons going back to D3D8 days for that). gs was available next in D3D10 and that's 2. Then the tesselation stages are 3 and 4, and finally compute is 5.
Since the D3D11 shader compiler can be used to compile downlevel shaders (down to SM2 IIRC) which can then be loaded by D3D9 programs, the order is obviously fixed for backward compatibility reasons.