Diana and Rageblade, skipping stacks

I just played against a Diana who could get 6 stacks on rageblade with 4 attacks. The one after her cleave was counting as (at least) 3 attacks for the purpose of stacking rageblade.

I reproduced this by simply entering the practice tool and buying rageblade. Had no abilities leveled, was level 1. It works.

I assume this is unintended.