Dropping after the fact still means it was recorded, this violating two party notice statutes.

Does that mean that every phone recording audio to detect its assistant trigger phrase villages two party notice statutes?

Yes.

These assistants have been around for a while, seems like that would have been established in court if it was the case.

What if it was never written to disk? The identification and trimming happening before any audio is actually saved.

Is picking someone else up on microphone at all a violation of two party consent? For example walking past someone in public with a loudspeaker call active.

I think there is even legal precedent for that. Dragnet surveillance recording of all phone calls. It was argued that recordings are only "stored". Judge order is needed for "retrieval", that may be several weeks later.