You’re probably participating in 100 or more A/B tests per year without knowing it and getting nothing in return other than a minor contribution to the company’s internal knowledge about what customers like.
Using feedback on your sessions makes that session, and presumably all attached data, fair game for training.
They explicitly ask, after the rating, whether they can look at your chat. You can just say "no" to that, if you believe that they are following the rules they say they are.
Your original statement of "using feedback gives them permission to train" is just plain false.