Privacy

This is a curious but not a very effective way to test. It's subject to several biases and the possibility that you happen to notice an ad related to your test topic that you wouldn't otherwise have noted. It's similar to how fortune tellers find ways to connect common patterns to an individual and make comments all seem like they could apply to you, but with ads and a topic.

With modern phone OSs, the concerning behavior also very challenging to technically achieve. Microphone enforcement is handled by the OS, so at the very least you'd probably need collusion, and that's not including the impact on battery life having the phone application processor on all the time.

Heres an easier way to find out:

Yes it is

To test if your phone is listening to your conversations, start by openly discussing a unique topic that you’ve never searched for or discussed previously while your phone is turned on next to you.

Let me stop you there. What about your TV, Internet-connected fridge, your Alexa device, your baby monitor, your security cameras, your voice-enabled fitness tracker, etc... ? Those could also all be listening to you. You'd never know which device is the real spy, so assume they all are.

I wouldnt know. Havent see an ads for ages.

One day you’re talking about a random topic while your phone is next to you and the following day you notice ads start popping up related to that same topic.

Joke’s on them ; I haven’t seen an ad in the last 5 years 😆

great. now all I get are butplug ads.