A friend demonstrated me this with her Google Pixel. We talked for a bit about a very conspicuous topic in presence of the phone, and the Google app (which shows a news feed when you open it) started showing articles relevant to the topic within a few minutes. At that point I believed her that her phone is listening, though I didn’t make a big deal of it because she did not make an effort to configure her phone not to.
I doubt they have such a good recognition model for Greek, plus my DNS blocks Google at that level, and I have a Xiaomi phone. Not that it's impossible, but it's less likely, plus the battery would die quickly.
