Thanks for these links.
I think many of my questions were poorly worded. I understand apps will track you / build behavior profiles when you're logged into them, and that each is sandboxed and unable to access eachother at the OS level. ie: Facebook would not see my Google Meet data on the phone, or browser bookmarks, etc ..
I'm more interested in understanding what (if any) hardening has been applied in GOS to defeat cross-app identification. ie: advertising profile building. For example if I'm logged into FB (and comment/like a post about puppies), and also logged into Amazon or Google services ... both those services would see that interest based on the shared trackers built into those apps, correct?
What if I've swiped up to close Amazon or Google App? . . . how 'closed' is the app?
For example. FB lite has 0 trackers
But that doesn't mean it isn't tracking you. You've signed into the service as a unique individual, and all behavior, likes, activity time, etc.. is tied to your unique account/identity. So it's still building a profile off your actions, it doesn't need additional trackers to do so, and GOS can't stop behavior that you're giving within the service.
So let's say I sign out of Facebook, it's closed, and I have to take an Uber someplace ... FB shouldn't be aware I've traveled to a new location, but Uber has FB Flipper and other trackers.
So even though I am signed out of FB, Uber is providing this info, and my habits/location are still being sent to FB... which I assume they have linked to the same unique profile, even without me being signed in.
It doesn't seem to matter if it was installed on the same GOS profile, or different ones ... there is no isolation, because the data-linking is happening service-side, based on behavior outside of GOS. In fact, using two different GOS profiles in the scenario above would break the isolation between profiles by tying them to a single unique user.
I understand it is impossible to avoid all tracking and advert profile building. I would simply like to understand where and how it is happening so I can avoid it when I need to, like searching for a surprise gift for someone, not having ads for related products appearing the next day, etc..