Nihilus ability drain force doesnt count plague as debuff

Captured some footage which proves that Nihilus ability isnt working as intended. Play close attention and you will see that the effect didnt get resisted (nihilus cooldown increase cant be resisted anyway) - which means it was only the 50% basis chance and it didnt proc. But on debuffed enemies the chance to reduces cooldowns should be 100% - so obviously plague doesnt get recognised as debuff.

Only posting the screenshots here, but i got it on video as well.

Edit: spelling