This!
I do work in IT security and my sense is that if your a target for the various three letter agencies, then yes, your phone, Alexa, RCS messages, SSL traffic can ALL be broken and monitored. Even if your phone is sitting passively on your desk - That's the "CAN" part of the conversation above.
As for "DOES" noted above, my sense is that breaking good encryption is hard (by design) and even nation state actors have limited resouces to do this, so "all" conversations near ALL passive phone aren't just routinely monitored, there just isn't enough bandwidth in the world to do that. - And voice agents, aren't just streaming everything to Google, Amazon, Apple, - ALL the time, without a wake word - Folks have actually tested this, and look at traffic monitoring.
That all said, three letter agencies, do routinely electronically monitor text and email comminications (especially traffic crossing borders) and have "keyword" monitoring tools monitoring nearly ALL that traffic. If you trigger a keyword that's running in automation, then you may get a bit more "study" - Sort of like how Gmail "reads" your gmail traffic and makes suggestions about appointments for flights, etc. - Just done on a different set of keywords and done on nearly all international traffic.
But again, I don't believe large tech companies are streaming all VA sounds back to their mothership for AI training - There are real bandwitdh limits here, for that to scale - But everything you say after a wake word (even triggerd by accident), is certainly fair game, and I certainly would expect it to be used in AI training, and potentially any court cases/foul play investigations.
So CAN everything be monitored - yes - even your local rPI or HA Voice Assistant (read up on NSA tailored access programs and HW implants) - But that's DOESN'T happen often for everyone. You need to get into their crosshairs, for nation states, and why would tech companies every bother, when they can just monitor your voluntary interaction with their apps.
JMHO