Seems to me like if it is 419k for r13 to r14 it is because the expected honor for a person at r13 is 419k so it gives you your bump in CP if you achieve that. Because there is no rank higher than 14, you cannot get an extra bucket.
This is counterintuitive because when you are r12 you need to get the r14 expected honor to get the honor from that bucket, which is 500k.
Which is to say you get your current next rank (r+1) bucket if you exceed your current ranks minimum expected honor. In this case r14. But you get your r+1+1 bucket. when you exceed that ranks minimum expected honor.
That or it is an off by 1 error on some array 