Apple could, sure, but we’d know about it if they were. Project Zero would have already publicized bug reports, and you wouldn’t hear the end of it from Android users. Plus, privacy seems to be where Apple thinks it has a definite advantage over Google, so I doubt they’d sell out for some ad revenue. (Where even does Apple serve ads? The App Store? In terms of Apple and advertising [the real money, at least supposedly*, in tech surveillance], Apple is more of a buyer of advertising than a seller of advertising.)
* I suspect that all of Facebook’s and Google’s data isn’t actually all that useful, and that we, as a society, and especially venture capitalists overvalue the predictive value of personal data. Certainly, network television advertising rates still go for far more than the race to the bottom that is online ad impressions. And Google has a hard time keeping mainstream advertisers happy with YouTube, hence all of Google’s concerns about monetization on YouTube. Clearly, the YouTube offering just isn’t as appealing to advertisers as the network TV offering, and who even watches network TV anymore?