Illaoi's E does not "tag" an enemy

So this has happened now a lot more often so it is an issue

I (E) someone only to

1. have to run
2. Someone else kills them

When they die within the kill/assist time frame Illaoi does not get credit.

I just did a game where the junger tried to gank me top and I E'ed him then ran circles around the turret kill it killed him. Games says Execute

WTF