If true it could have quite an impact.

Everyone I think assumes training in the general “it affects the distribution” sense. But if it fishes precise novel insights out as alleged then it makes these products dramatically less valuable. At least the non zdr ones

This is a problem with every technology product. Before Facebook and Gmail had strong institutional controls, any employee could just open anybody's email and private messages on a whim. Now things are a bit more strict for random employees, but if the company as a whole wants to do something, you bet they can.

Can you opt out of sharing data for “analytical purposes”? I think you can’t. And what does “analytical purposes” even mean?

I think people straw man the whole data argument on “opt out of training purposes” and ignore the mandatory analytic purposes. Which probably includes figuring out trends and important research problem data to steal from users and even business ideas.