You are correct to a degree. AdMob is now owned by Google. By allowing AdMob to collect analytical data from iPhones you are giving Google and the android platform free information on iPhone users.
Unless someone can post a link to where AdMob gives Apple all the same info about Android phone users I keep my opinion.
I see where you are going with your argument however the difference is that in cars anyone can get a car take it apart, do surveys, contact suppliers and get all the information they need (the government also regulates automobiles so they have a ton of info the public has access to.) Apple is a closed platform which limits that. Personally, I could care either way I see Ads as necessary (it keeps costs down nothing in life is free) and I don't care who gives them to me.