> Email and phone calls are considered confidential, even though it is possible for vendors to inspect the communication.

It's a weak analogy. Ordinary comms infrastructure providers actually have pretty robust policies, technical, and contractual measures in place that restrict employee access to customer communications. In contrast, in the wild west of generative AI, companies actively monitor session data for the content itself, in order to exploit it for their own business purposes. There is zero expectation of privacy.

So I don't share your expectation that precedent will uphold the use of consumer-tier services (in their current form) for handling privileged material.