Sorcerer Skill Bug

I am playing Sorcerer in S13.

I find one skill confusing. I am not sure if the skill is meant to work this way, but if i read the description it seems it is not working as intended.

The Skill in question is Familiar>Bonus Effect> Fast lightning (Shock skills that does lightning dmg)

The Bonus Effect states:

Fire Familiar - Gain 5.0%(+) Healing……..

Cold Familiar - Gain a barrier for 5% of Max Life….

Lightning Familiar - Reduce a random active cooldown by 0.5 seconds.

Now if i have Fast lightning chosen then the I get no cooldown effect on my Ice Armour that is on cooldown.

Instead if I have the skill setup as Familiar>Bonus Effect> Prismatic Familiar (Pyromancy/shock/Frost skill) then I see my Ice armour cooldown reducing.

Is it meant to work this way?

The way I read it, if Familiar does Lightning damage then I should get cooldown. But it is not working this way.

Can you please check and verify if it is a bug or if it is meant to work this way.

Regards