The node_keying_matte.blend test is very sensitive to the exact pixel values in the input image. It is hard to match the output between SSE and non-SEE codepaths of sRGB-to-linear conversion, especially when it is done form the OCIO side. Note that even without OCIO the match could be very difficult to achieve, since BLI also implements SSE optimization (although, we are in better control over there, so might increase the accuracy). Ref #110685 Pull Request: https://projects.blender.org/blender/blender/pulls/110897