Why can't Nasus stack Gangplank Barrels and Inhibitors

Nasus can stack almost everything, alive or inanimate, in the game with his siphoning strike (Q).

But he can not stack GP barrels or inihibitors. Why is that? Can this be fixed? Nasus can stack Kalista's ghost, Yorwick's spirits, Heimer's turrets, Ilaoi's tentacles, Shaco's clone, and all generated objects or creatures from champions.

The inhibitors always bothered me too, since he can also stack turrets.