I have a question regarding her ability to punish glancing.

As it says above she places sand debuff whenever they glance which is cool, but you can’t turn it into passive because it also glances. Which makes this ability basically useless because the sand debuff is just gonna fall off in 3 seconds so what’s the point?
Is this intentional cause it just doesn’t make sense to me? I was fighting a Sersi if that helps, who just gonna be glancing 80% of the time.