That is not true. Google retrains its models periodically. Removed data is not used for training models. Also I'm not sure that private user photos can even be

That is not true. Google retrains its models periodically. Removed data is not used for training models. Also I'm not sure that private user photos can even be used for training cross user models because I don't see how these photos could possibly be disclosed to raters, so there would be no ground truth.