The top comment in the video mentions someone's experience with resistor binning with a batch of 10% resistors having no samples under 5%. Anyway, the resistors

The top comment in the video mentions someone's experience with resistor binning with a batch of 10% resistors having no samples under 5%. Anyway, the resistors binned for tighter tolerances aren't going to have to have a trough in the center of the distribution - they'll have cutoffs on either side. Binnig can be repeated for any tolerance desired, so carbon vs metal film doesn't have anything to do with it.