This is one of those things that people do a doublethink on in modern society. Almost everyone, at least those that I've talked to about it about will tell you that they have had a moment in their lives when an advertisement was shown to them after they said something in real life, either near their computer, phone, smart device or whatever. But when you start to turn off your devices when talking about things, you become a paranoid nutter. These applications have had keywords that they pick up for a decade now. They are always listening. Is it really ridiculous to think that they could have other keywords that they can recognise? Even more so with artificial intelligence.
It's such coincidence that you said this, I was thinking earlier about whether bringing a smartphone into the confessional can get you excommunicated.
I have seen what you describe several times. You are talking to somebody about a certain subject, and then they open their phone and there is an advertising about that very subject.
I don't think that it can get you excommunicated, but it is certainly imprudent.
The advertising thing is what we know. Imagine what they hear and we don't get to know. I have never liked this smartphone thing, even from the very beginning.