"The problem with this kind of aggressive A/B testing is that it's a game of "how far can we push the user?""

Google also does this with Chrome. Users are subjected to "field trials". No explicit consent is requested. Most users are probably unaware. While it is possible to see which trials one is a part of, Google is not transparent about what exactly these trials entail.

https://www.ghacks.net/2013/04/05/field-trials-in-chrome-how...

https://textslashplain.com/2017/10/18/chrome-field-trials/

https://chromium.googlesource.com/chromium/src/+/master/test...

https://blog.chromium.org/2012/05/changes-to-field-trials-in...

http://raeknowler.com/wtf-chromium