Tl;dr: The trouble with ntile seems to be that, when the author of the post imagined what it did based solely on its name and she imagined wrong, she ran with her imaginary version way too long before checking the documentation, which was very clear about its behavior:
> Unlike other ranking functions, ntile() ignores ties: it will create evenly sized buckets even if the same value of x ends up in different buckets.
> Unlike other ranking functions, ntile() ignores ties: it will create evenly sized buckets even if the same value of x ends up in different buckets.