Yes. If I remember correctly (I could easily be wrong), it was this way in DotA because the spell was far too complex and thus was handled 100% by triggers. Because of this, it lacked and still lacks a status debuff icon entirely. As most people have said, it has carried over like it is from DotA, just that the HoN engine is flexible enough to provide us with a little status icon for it.
I assumed this too
I also assume this is the reason why Demented shaman's slow isn't purgable either.