Let's understand what we are talking about here -
1) On android phones - the moment you say, "Hey/Ok Google", Google starts acting based on your voice commands, i.e. becomes voice-activated.
2) On observing this carefully interaction carefully - users are compelled to think that probably Google is listening to all my conversations, and hence was able to catch the "Hey Google" part of it instantaneously.
3) This comes as a big unwanted surprise for the user who thinks this as a privacy breach. (Although legally while setting up the phone and accepting multiple fine-printed terms and conditions, s/he would have said yes to this interaction and google might not be actually sending all of the data to its servers). Good read
1) As a good interaction practice to aid users being comfortable about their data and privacy - shouldn't the interaction at least warrant the user to click on an icon or tap at a particular place etc. to activate this voice setting? How about something as simple as "Tap home button thrice" or something that is easy enough say when you are driving?
2) Can this be termed as dark UX?