That doesn't seem quite right. Shader model 4 doesn't support UAVs unless "ComputeShaders_Plus_RawAndStructuredBuffers_Via_Shader_4_x" from D3D11_FEATURE_DATA_D3D10_X_HARDWARE_OPTIONS is set. We currently set that when we have at least WINED3D_FEATURE_LEVEL_11.
Thanks, sent a v2 that makes this an 11.0 feature instead.