Fiora's Passive doesn't appear in bushes.

As Fiora, if you hide in a bush, and an enemy walks by you, your passive won't appear on them. You have to literally give them vision of you in order for your passive to start appearing.

Now, I can imagine that this is so the enemy doesn't know you're near, but can't we just make it so the enemy can only see your passive when they have vision of you, but still let it appear for yourself?

I'd like to be able to ambush someone and actually proc my passive, and I can't, because it won't appear until they see me.