This is a court issue, not a technical one. This has so many side effects that weren't thought through (Using Gmail to draft a letter to your attorney, but gmail has enabled AI editing...).
Seems dumb, and like it will cause quite a few issues until it is overturned.
Why would this be overturned? AI is not a lawyer, it can't have attorney-client privilege. In your scenario, you're sending an email to the attorney, not chatting with a chatbot about your case.
Intent matters, though. Accidentally divulging information you intended to send to your attorney is one thing, but if you are deliberately sending it somewhere else it's something different entirely.
Non-lawyer discussing their lawyer's communications with a third party has defeated attorney-client privilege for eons, and that's basically what happened here. Especially when you're sharing those communications with a third party who explicitly told you that they will share those communications with the government if the government asks. There's no reason to overturn this.