Azir's soldiers don't damage Teemo Shrooms

The following situation happened:

I played a pink ward ward in the upper lane bush of the midlane. It made a Teemo Shroom (R) visible. I made a (formerly) spawned Azir solider (W) attack it.

The attack animations went through, none of the attacks dealt any damage to the Shroom.

Assumption: Azir's soldiers replace his auto attacks with spell damage. I assume that Teemo Shrooms were made invincible to spell damage. however, considering that Azir's W completely replaces his auto attacks, thus rendering Shrooms wihtin his soldier's range invincible to him.

I believe this should be fixed for 2 reasons: 1.) Using Azir W uses his auto attack command thus should interact with shrooms as such since it does with wards. 2.) If they're invincible and are to stay so he at least shouldn't be able to attack them since it's broken that it disrupts the attack move command.