Sejuani's E ability feels bizaare in terms of design

It's an ability that has a passive that applies a debuff that doesn't do anything until activated. Then, when activated, it deals a tiny bit of damage and slows.

But Sejuani's theme is a frosty pig-riding Tank with an ice flail. You would think her abilities would already passively slow, but they don't.

It's thematically confusing, and IMO a strange mechanic that takes away from her kit. When I'm swinging my ice flail around and seeing frost everywhere, I expect to be slowing my opponents around me, but I don't until I hit that button and it feels extremely unimpactful compared to Q and R.