Illaoi spirit is targeted by turret before attacking enemy champion.
When Illaoi pulls a spirit into a friendly turret's range, the turret will target the spirit and attack like normal. However, if the enemy champion (whose spirit was pulled out by Illaoi) attacks Illaoi under the turret, the turret WILL NOT switch targets to the attacking enemy champion.
I'm not sure if this is intentional or not, but it seems as though the turret should switch from the spirit and target the attacking enemy champion, as it switches from a minion to an attacking enemy champion. Also, pulling a full health spirit under a turret would basically act as a free opening or the enemy champion to step in and attack.
I have only seen this once, so I am sorry if I a mistaken, but I'm pretty sure what I stated above really happened.
Thank you for your time, Materializer (phoenix7778)