I think there may be a fear that if the face is too static, it’s not going to look real, so they over-animate a tad. On the flip side of the coin, I think Disney once got some critical flak for the human characters in Sleeping Beauty being too stiff, when the animators were trying to be more realistic.
Having seen R1 twice in 70mm IMAX, Tarkin looked good to me. Is there something about putting the images out onto film that makes it less digital looking, or am I simply perceiving it that way because I know I’m watching a print?