Ekko able to use blink part of E while rooted

I was playing as Rengar in a normal 5v5 match earlier today, and there was an Ekko on the enemy team chasing me. I turned to use my empowered Bola to root him, which connects. He had either just used the "roll" part of his E or was in the middle of it when the bola connects for the root. So I walked a bit closer and he blinked to me for the kill with the second part of his E despite the root. I'm not sure if this is intended as a "queued" ability if he was already in the middle of the roll when the root hit or if it's an unintentional interaction. Either way, I thought I'd report it! Thanks.