Earlier quoted context omitted.
How is any smart phone that supports OK Google and Hey Siri different from an Echo in this respect?
It's not. I think the poster may be confused about how the Echo works - it's not constantly streaming audio or transcripts back to Amazon, just when it's directed to do so via the "Alexa" trigger word. You are absolutely not consenting to send full transcripts of your conversations to Amazon. If they are in possession of it, it's entirely illegal, and the third party doctrine doesn't apply.
This isn't Apple fighting encryption backdoors. This is Amazon impeding justice.
"1.3 Voice Services. You control Alexa with your voice. Alexa streams audio to the cloud when you interact with Alexa. Alexa processes and retains your voice input and other information, such as your music playlists and your Alexa to-do and shopping lists, in the cloud to respond to your requests and improve our services."
https://www.amazon.com/gp/help/customer/display.html?nodeId=...