Yes, with np.linalg.norm I can substitute part of my code:
from:
- np.sum(np.sqrt(np.sum(np.square(a-b),axis = 1)))/3
to: - np.sum(np.linalg.norm(a-b, axis = 1))/3
which both yield 0.5015439217802148 as the error.
However the way, the error is computed on OpenCV: Camera Calibration
still differs from this approach and yields a different error (0.31797973380564853), which in my opinion makes little sense.