Facebook also has a button next to ads saying why you were shown the ad. What does that say? Also the causation might be in the other direction. You and your correspondent might have seen an ad that then caused you to have the conversation.
So I messaged my agent and said "i love the apartment but the windows don't have any gates or safety catches, my understanding is gates are pretty expensive, would it be possible to atleast get safety catches on the windows?"
Never googled or anything like that. For the next couple of months I had constant adverts for windows gates in Facebook.
And do you and your landlord have the same internet connection?
How did you know gates are expensive?
So today my wife and I were looking at dogs that need forever homes using her laptop
Later I got a dog food ad on my laptop that specifically mentioned shelter rescue pets. I haven’t used any of my devices or accounts for dog-related searches for at least two months.
It doesn't match you exactly to the other persons behind the same NAT, but it adds some information, raising the likelihood of ad coincidences a little. I have no idea how much. It's likely to depend on which IP address, and other tracking statistics.
If you have diligently blocked lots of tracking state, then IP address will be a relatively stronger signal, and this might (ironically) increase the likelihood of ad coincidences.
Also, WhatsApp is definitely e2e encrypted. I worked there and saw the implementation (and the difficulties it causes for things like blocking spam/nasties) myself.
This was 1 year ago.