||ok let's say i grant you that it's technically feasible to do your conspiracy theory about audio to text ad targeting from other people's phones.
i still think the conspiracy would be too large to keep secret.
there'd be too many integration points. you've got to get that code compiled into the app before it goes to the app store. so somebody that's like the sole person responsible for building and sending the app to Apple for validation and is obviously integrating with the other legitimate engineers on the rest of the app is definitely going to need to be a double agent of sorts, clandestinely inserting the extra code that does the nefarious audio to text listening.
then you're going to need your own secret team of engineers, testers, product managers, managers, and designers to actually build those features. and besides building them into the app, they will need to work on integrating them into the actual ad targeting products on the other side that will exploit the audio to text they've captured. so the ad team needs to also be in on it, or you're gonna need another double agent working for you there. if that code isn't compiled and deployed as a binary, then you've got extra problems.
you're going to need to somehow always update the source in production independent of what the other engineers think they are pushing to production.
like they'll push and then the secret team grabs it and adds their own diffs utilizing the secret database of audio to text data.
so you've got more engineers that do ad targeting stuff on top of your secret iPhone and Android app teams.
i don't think you ultimately get away with the conspiracy with any less than say 100 co-conspirators minimum.
all of them will need to be loyal for life.
in addition they'll need to be lucky enough to never get caught making these changes to the products.
and the reward from doing this will need to be great enough to take on that risk, unless we just think these conspirators are stupid and taking risks they shouldn't be.