The title animation is actually by Yuta Matsumoto, one of the 3D animators in the opening. The guess for the traditional part is based on the fact that Maki Yamakoshi and Daichi Kobayashi are the only KA credited for the OP. The latter is specifically listed as Millepensee member alongside people in other positions, and since they likely worked together and there are multiple colorists, it'd make more sense if they handled the smaller 2D bits throughout the sequence.