Rihawf thought you were trolling, but in reality, you're just incorrect.(if I say dumb you'll report me)
Tell me how i'm incorrect. I play fiora and block all kind of onhits... wukong, jax, GP ect.
Because you are misunderstanding the complaint and what on-hit effects they are talking about. The complaint is if Fiora blocks the attack, why does the silence from Garen's Q still apply. Same with Wukong's Armor Reduction, GP's Q's slow, Udyr's stun. Fiora's W blocks the physical damage, but not the on-hit effect.
Additionally Fiora's W does not block magical portions of on-hit attacks like Jax's W and R, Teemo's E, and attacks that convert on-hit physical damage to magical damage like Poppy's Q and TF's cards.