Firebase Analytics first_open event has update_with_analytics = 1 after iOS device reset — why?

I’m using Google Firebase Analytics on my React Native iOS app and I’m seeing an unexpected behavior with the first_open event and the update_with_analytics parameter.

According to the Firebase documentation, the parameter update_with_analytics is sent when Analytics is added to an app that was already installed on the device (i.e. Analytics was not present at the time of the original install and was added later).

However, my case does not match that scenario.

Important context

• The app is more than 2 years old.
• Firebase Analytics has been integrated in the app since the very first release.
• Analytics was never added later; it has always been part of the app binary.
• The iOS device is fully reset using Erase All Content and Settings.
• No iCloud backup is restored after the reset.

Observed behavior (scenario 1)

1. The app already includes Firebase Analytics.
2. The iOS device is fully reset.
3. No iCloud backup is restored.
4. The app is installed again from the App Store.
5. On first launch, Firebase sends a first_open event where
   update_with_analytics = 1.

Based on the documentation, I would expect update_with_analytics to be 0 in this case, since:

• Analytics is already present in the app binary.
• This is a clean install on a freshly reset device.
• The app was not upgraded from a non-Analytics version.
• No iCloud backup was restored.

Additional observation (scenario 2)

If, after the device reset, the app is deleted again and reinstalled once more from the App Store, then on the next first_open event:

• update_with_analytics = 0

So the behavior is:

• First install after device reset → update_with_analytics = 1
• Subsequent reinstall from the App Store → update_with_analytics = 0

This makes the behavior even more confusing, since both installs are coming from the same App Store binary and both include Analytics.

Question

Why does Firebase Analytics send update_with_analytics = 1 on the first install after an iOS device reset, even though Analytics has always been part of the app and no iCloud backup was restored?

Is update_with_analytics actually triggered by conditions other than “Analytics was added later”, despite what the documentation suggests?

If possible, I’d appreciate clarification on what actually causes update_with_analytics to be set to 1 for first_open events on iOS, especially in device reset scenarios.