Yes. IDFA's full form is "The Identifier for Advertisers" which is generated by OS itself. Think of it like a proxy of IMEI number itself (back in the old days IMEI itself was used instead of this).
All of the Apps get the same ID and that's how your "persona" graph is constructed.
Sidenote: One of the bets people are making with this change is that now free apps will start forcing you to signup (via email/mobile number) which will be used to construct this "persona" graph again because who has time to create new emails for these purposes.
Well, your phone has the time to create new emails for these purposes with the Sign In With Apple feature[1]. You don't have to remember your email nor your password because iOS can create a secure one and save it on your phone. More secure than people using the same email and password across multiple apps imo.
I mean that they also saw the reaction to that change coming, ie. they realised if they got rid of the advertising ID, it would make apps force you to log in. I'd be impressed if that was deliberate, but it could have been.
My 10 year old gmail account has no associated phone number. Maybe it's valuable now. It's the only thing I use at all that is a Google product, and I'm always near deleting the entire account but it's just so convenient (Read, I've been lazy)
Regarding your side note. Apple is also, more and more, requiring you allow the login with Apple button. This would effectively shield most of the data off if you want.
Interesting workaround. I imagine this could in turn lead to more pressure on these same apps to implement Sign In with Apple - as a user, its email privacy feature becomes more interesting in this scenario.
> more pressure on these same apps to implement Sign In with Apple
Afair this is actually a requirement: if you have email/facebook sign in option, you need to implement Sign In with Apple as well
I use email aliases to sign up to services for this reason exactly. There is no way to link the aliases, and so tracking is limited to the registered site only. The Log In with Apple solves this more elegantly
Sign In with Apple is not a panacea. UPS on-boarded me a couple of weeks after my initial registration, and the two services I’ve used it for (UPS and Etsy so far) have received my name from the initial registration process (a radio button selection and a bioauth).
I wouldn’t treat it as a privacy feature, I would treat it as a convenience feature. When I needed some extra mask straps, I installed Etsy, didn’t previously have an account. So I used Sign In with Apple to register, picked out some mask straps, and Apple Pay to pay. The whole process only took as long as it took for me to make a selection and two biometric authentications, but some of my information had to be exchanged in order to make that transaction possible.
Also I can login to UPS and Etsy without a password.
All of the Apps get the same ID and that's how your "persona" graph is constructed.
Sidenote: One of the bets people are making with this change is that now free apps will start forcing you to signup (via email/mobile number) which will be used to construct this "persona" graph again because who has time to create new emails for these purposes.