Yes, there is no upside for them to explicitly say you can opt out of training using these methods if it's not true. They are already facing copyright infringem

Yes, there is no upside for them to explicitly say you can opt out of training using these methods if it's not true. They are already facing copyright infringement lawsuits, and clearly more will come, so if they were lying about this, it would come out in discovery, which would be devastating. So, basically I'd say you can trust them about this because it would be very much against their interest to lie.