If you believe that Google's just going to brazenly lie about what they're doing, what's the point of changing the settings at all then?

In fact, Google is subject to various laws and they're subject to concerns by big corporate customers, both of which could result in big trouble if they end up flagrantly and wilfully misusing data that's supposed to be private. So yes, I would tend to believe that if the feature doesn't say the data is being used for training I tend to believe that. It at least behooves those who claim otherwise to come up with actual evidence of their claims.