I'm not saying that Anthropic and OpenAI are definitely dishonest, there is no proof of that. However, when you have

1) an extremely high financial incentive to be dishonest (trillions of dollars),

2) low-ish chance of being caught, especially if you launder the data through another model to remove identifying information,

3) the people in charge of said operations are generally agreed to be snakes,

then it should at least arouse suspicion. You may be right that get enough data from opt-ins that they don't need to do it. I do believe that they don't violate enterprise ZDR agreements, but for normal subscriptions I'm much less confident.