Projectile Protection is Faulty?

I know Projectile Protection is supposed to lessen the pain from any sort of projectile: (Arrows, Snowballs, Eggs, Fireworks, Shulker Bullet, etc.) But from the official books apparently they're supposed to rebound arrows, this may be a misunderstanding, but that would be better than getting shot by a Harming II arrow whilst on fire and being cut by a raging child