Killing GP's barrels doesn't give Nasus stacks.

I find this kind of interesting because Nasus gets stacks from killing a ward with Q.

Also, Yorick's ghouls are pretty much minions... So I don't see how that compares to it. Does Nasus get stacks from Zyra Plants or Shaco boxes or Teemo Shrooms or Jhin Traps?

Nasus gets stacks from everything, including Teemo shrooms, Shaco boxes, wards, Illaoi tentacles, Yorick ghouls etc. GP barrels should give him stacks, I simply don't see why they shouldn't at that point

GP barrels don't officially count as units and you don't get CS for killing them.