Why can Aphelios use Q while low on Ammo

(Played on Pbe today.) I mean the description on q says it needs 10 ammo and 60 mana to cast. But Aphelios can cast it while below 10 ammo. Isnt this op, the player doesnt even have to think how to press Q properly, gets below ten Ammo and anyway can press it without thinking? He can be literally on 1 Ammo, cast Q from weapon 1, it switches to weapon 2 automatically, and he can cast another Q again, then switch to additional weapon and cast Q 3 ? Lul ok. Is this a bug or intentional