Earlier quoted context omitted.
This was my thought too; there doesn't seem to be a way to verify this isn't happening.
If data is being buffered and only sent after the trigger words wouldn't the data transmitted vary depending on how much was said before the trigger word?
What you should be asking with any "smart" device is "can I prove this device will do no harm to me".
Honestly I have never understood the value proposition of any smart device. Why would I want any of that functionality? Never once in my life have I ever wanted to talk to my TV. I'm beginning to (again) question the wisdom of carrying a smartphone.