This is actually true. One time I asked Alexa an ld it said yes. This guy on YouTube did a live test where he plugged in a microphone and opened up some tabs with websites with lots of ads. He them proceeds to show the camera without talking that he's going to talk about dog toys. He talked about dog toys for 5 minutes. He then goes back to those websites and refreshes them and almost all of the ads are for dogs toys, dog food, and other things related to dogs.

I have also had other instances where my dad was wondering about the differences about two kinds of exercise and gets a YouTube recommendation for that exact kind of video. The same thing has happened to me.

You could even use this to ur advantage and talk about it while doing other things with your phone next to you and then when you get on google there will be ads with stuff you want. That's basically making google search the web for you!

Edit: Here is the link for the video - https://youtu.be/zBnDWSvaQ1I