I’m aware of how they rationalize it, and it’s bullshit. They compare themselves to a router that passes through packets unmolested. But that argument is trivially refuted by the fact that their IPs are what their customers' DNS queries resolve to, and the fact that without being explicitly configured to do so, their proxies will not serve content on behalf of an origin. L3 routers simply copy packets between interfaces. A CDN is significantly more complicated than that.