Ever wonder how long our "projectiles" have been around: https://ordonews.com/archaeologists-confirm-16000-year-old-idaho-stone-arrowheads/
You are correct - and the art of casting a projectile (hard object) is historically interesting: https://www.americanoutdoor.guide/features/blowguns/Calling a arrow head a pellet is a pretty broad terminology, you might as well call the first rock thrown a pellet.