nose_tip from model_points[0] while the first vertex is lips tip in canonical face obj

[chojuahn]

Thanks for the great work.
I'm trying to figure out why model_points[0] represents nose_tip while the first vertex is lips tip in canonical face obj also in canonical_metric_landmarks

in face_geometry.py
canonical_metric_landmarks = np.array(
    [
        0.000000,
        -3.406404,
        5.979507, ...]

also in canonical_face_model.obj
v 0.000000 -3.406404 5.979507

and mediapip canonical face model uv visualization also has the first vertex as lips tip.

While the nose tip should be model_points[1] following the above references, how come head_posture.py draws a line steming from model_points[0] correclty put on tip of the nose when I test it?