Because that’s the length of the iterator? The range is empty, its exact size is 0.

The range is invalid, not empty; someone had to do a validity check to return 0 to prevent it from returning -5 or trying to count up from 0 (depending on what it was willing to assume). A big point of the article is that a range of size 0 should always be iterable, but it somehow isn't, because it isn't actually of size 0.