Billy standing animation are fine considering that Clark has the lowest amount of animation in his stance than billy, billy, king, kim all have an average of 9-10 frames in there standing animation, Characters like Ralf have over 30+ frames.
It's less about how many, and more about how they're used, for me. Clark's rotating arms, and the smooth animation of Kim's Gi all look like nice, well-defined animations, with elements of limb rotation, cloth deformation, etc, to make them look kinda complex. Billy has some of the stiffest-looking, straight-down arms in the game, which is just a bit odd. The few intricate things they added to nis animation, being his finger movement and SLIGHT diagonal shift of his staff at one point, just don't stand out. If they made him bend his arms at the elbow, so his lower arms could raise and play with the perspective just a little bit, or make his breathing animation in to a "hopping back and forward" type motion, that used more so the same frames, but gave a little sway to the back of his bandana, plus add a little rotation to his feet / lower legs, to show the press-back and leap-forward motion, then that would have made him look a bit more lively.
Nothing that'll keep me from playing him or anything, but there's a lot of "Billy looks half done!" commentary out there, and I think the base of those thoughts are set by his stance, and maybe the fact he's missing his counters.