Leona's E is not a root. It's a stun.

you have to have downs to think its a root

I like you. You make me feel better about myself.

As someone who both plays Leona, and Morg, one of her biggest counters, it's a root that REALLY FEELS like a stun.

Since you are so quickly hit by her Q after the E it's easy to feel like it's a stun too, especially since Leona generally comes from outside an auto-attack range so it feels like you don't have anything you can do. But here's where Morgana comes in, one of the best moves you can do against a Leona with her is let her land E on you and drop your spellshield while she's in transit to block her Q and punish, so it's totally a root.

Unless you mean it RECENTLY has become a stun over a root, because I haven't had that matchup in the last patch or two, the topic makes it sound like it's been your general experience.