But how would down sizing a breaker make this rule apply?There was a time when the NEC did limit the need for upsizing the EGC to instances when the ungrounded conductors were increased because of VD considerations. But I think there was a bit of abuse going on, as in, "I didn't use the larger wire because of VD. It was just what I had in the truck at the time." The rule was changed to require upsizing the EGC regardless of the reason that the ungrounded conductors were upsized. The oldest code book I have handy is 2008, and this change happened before then.