I think this is the kind of place where applying bounded distrust is critical: it's not whether we trust Google overall, it's about figuring out what sorts of statements we should expect to effectively bind companies and in what ways.

For example, I think a pretty worrying outcome here is that deidentification is imperfect (not surprising), the data is fed into model training, and then the model makes identity-dependent inferences. Since no one tried to break deidentification, it's within what I'd expect from the company. (And, to be clear, is bad.)

On the other hand, intentional reidentification to work around contractual deidentification to "a sell a product to the airlines that offered to keep annoying people like me from purchasing flights" is the kind of thing that would make Google's lawyers terrified, so we should not expect it.

If you look at how this worked with DoubleClick, Fitbit, etc there were initially barriers to linking data but the mechanism for unlinking was updated agreements with people who had ongoing interaction with the continuing entity. That's not the situation with the Spirit data.

The closest I'd expect to see for a "keep annoying people from purchasing flights" situation is not a list of troublemakers but a model that's very good at scoring future communications from customers, and has learned to distinguish profitable vs unprofitable customers. This is well within what I'd expect from companies, and doesn't require any reidentification.