Nunu's Rift Herald Bug

When Willump eats a jungle monster, depending on the type of monster that he eats, he gets a buff... But the new Rift Herald doesn't provide Nunu with anything. Is this a bug or is it intended?
[zombie-nunu-bummed] [zombie-nunu-tears] (sad Zombie Nunu and Willump want some Rift Herald's brain buff)