But even if was, then your logic would be absurd. You would be saying that every urban myth is true because a single example was true. That is nonsensical.
Let me spell it out for you: You claim that X is nonsense without any reasoning whatsoever. Why was NSA surveillance before 2013 not an urban myth? Why is facebook eavesdropping on you nonsense?
And no, I wasn't implying anything - I'd like some arguments regarding your point. And saying 'thats nonsense', 'you're wrong' does not make any of your points valid.
Things like Amazon Echo exist and are used for all sorts of purposes, including making purchases and being available for law enforcement.
Gmail is an advertising company who actively listens in on the conversations you have on on their services (i.e. gmail) and uses it to display ads.
Facebook is an advertising company and data mines the hell out of all the data about you they can get their hands on to be able to sell targeted ads.
The specific use-case of "listening to you talk with your mouth, analyzing it and then showing you ads based on it" might not be explicitly be mentioned in the Facebook TOS, but it's the very natural extension of their business model keeping in pace with technology.
If someone says that lizard aliens rule the world, then I don't need to prove or explain why not. I can simply say that it is absurd, and that such extraordinary claims require extraordinary evidence. Everything on this page has been "I talked about x and then I saw an advert for x a few days later". It's absurd cringe.
The OP did not make an absurd extreme claim. He or she asked for evidence attempting to diagnose whether it's true. You reject the commenters' anecdotal evidence.
But even if was, then your logic would be absurd. You would be saying that every urban myth is true because a single example was true. That is nonsensical.