With procedural motion (tails, etc.) I usually use Rig Attribute Wrangle SOPs, but I have been trying to move some of my setups to Rig Pose SOPs. However, the seemingly same expression behaves differently in the two. I am sure I am misunderstanding something, but I am not sure what. Maybe the translation-rotation-scale order is different?

sin expects a value in radians like this:

float rotation_angle = radians(5) * sin(radians(f@Time * 300));
prerotate(4@localtransform, rotation_angle, {0, 1, 0});