But that communication is clearly intended to be confidential. Also isn't having one attorney on a multi-party communication marked confidential sufficient to create privilege?

When I worked at two different FAANG companies, both legal orientation sessions taught this specific scenario as an example of something that's not attorney-client privileged.

If you email your lawyer to ask legal questions, that's privileged communication.

If you just cc a lawyer on a thread while you talk to other people, adding the lawyer doesn't make the conversation privileged or protected.