But does Twitter have a signed copy of all those agreements? No. How could they? Either they comply without hesitation to all takedown requests, or they don't

But does Twitter have a signed copy of all those agreements? No. How could they? Either they comply without hesitation to all takedown requests, or they don't take anything down unless ordered by a court. Doing something in the middle injects a level of moderation that goes against their "free speech" principles.