Doesn't mean it's not his Weakness
Or that Luffy can't Block any Cutting Attack
Cutting Attacks are Dangerous for anyone, not just Luffy
But the reason We call it Luffy's Weakness is cuz He doesn't have a Normal Body
He is Immune to so many things, but i explained how Oda insists that Luffy will never gain an Immunity to Cutting Attacks
For example, Crocodile is a Logia, He is Immune to countless things
But We say his Weakness is Water, even though He also can Block it (Easily actually)
But still his Weakness