Regardless of who is really at fault here, this isn't healthy for the GPU market. This "hardware favoritism" with DX 10.1, TWIMTBP program, and any other general favor placed on either AMD or Nvidia isn't good. How will PC Gaming, especially with the advent of the PC Gaming Alliance, ever reach mainstream respect if games favor one type of hardware to another?
And Assassins Creed PC already has enough issues. It's a sloppy port with questionable performance. A situation like this only worsens that deal.