Urgot Conqueror Rune bug

Helloo there! This is my first time recording a video so sorry for the clicking noises and all that.I found a bug on Urgot where the Conqueror rune buff is applied after 4 seconds in combat by urgot's "w" which is supposed to count as an autoattack as far as i know, but there is no true damage.It only works if it is applied by a normal basic attack.My question is: why does it proc when using "w" while giving no damage?If " w " was not supposed to proc Conqueror then it should not, but this procs when using "w" and gives no extra true damage , basically wasting it in fights.