That' s mostly correct. Minor corrections below:
- Case 1 & 2 are <iOS14.5. With iOS up to 13 around 20-25% and iOS 14.0-14.4 around 45% LAT rate
- Under iOS14.5, there are 2 layers: user can ask all apps not to track ("AAtRtT") at device level, in which case they don't get the app-level ATT prompt to consent or not. (Those users with AAtRtT=off will in 99% not give consent, yet there is an edge case with AAtRtT=off and ATT=on, and Apple mentions is in its Adservices documenation).
So you have 4 cases for your own app: AAtRtT=on/off + ATT=on/off, the latter being the one that matters to you.
- Then it depends what you want to use the consent for. Often, it'll be to track measurement through IDFA at user level, which supposes the other party (whether that's FB/IG, or another publisher, for instance another app monetizing through Admob) also has it, which limits your reach.
Say you get 35% consent from overall users (including old iOS13, AAtRtT=off etc), if the other party also gets 35%, that's a matching anywhere between 12% and 35%, although we can suppose to some extent it will be the same users who consent and deny in all apps.