NN predictions of τ from Planck 100+143 GHz data, resulting from training 100 equivalent models with different random initial weights and random seeds for training data, considering Gaussian two-channel training (blue tones) versus SRoll2 retraining (orange tones), and f_sky = 0.5 (downward triangles) versus f_sky = 0.6 (upward triangles). Colored triangle markers show the best-fit values for the single models and horizontal lines in the corresponding colors show the ensemble average of τ (middle) ± the 68% confidence interval (upper and lower lines).