The only person calling it stealing is the author of this article, so this is a pointless discussion. The majority of this thread is just arguing with themselves.
Stealing may be the wrong word, but I actually think this is important. I don't think the providers have been up-front about how we should be handling these thought signatures. A large system with a lot of users may be capturing these and even caching them to send them back with future requests. If data can be pulled out of these, then they need to be treated more like cookies than opaque, encrypted nonces.
They are also encrypting it so they must see some reason to do this. I suspect they think it is proprietary or otherwise a way that people can “steal” their implementations.