I occasionally do fun little experiments with others and there phones (with contest) where we find a subject we both have absolutely no interest in, and we figure it out without any electronics at all around, like our back and what not, then we agree to not do anything with our electronics about it at all and only talk to each other about it by our phones, and every fucking time we both start to get add recommendations about whatever we was talking about.

Had a past friend who was asexual and aromantic and never really cared or looked into paternity tests and baby stuff (because like why?) and after a few days of randomly talking about it they got tons of adds targeted for pregnant women (they was trans non binary but was afab)

So from my limited tests, it absolutely does spy on us