UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:64.0) Gecko/20100101 Firefox/64.0
Platform: 11021.56.0 (Official Build) stable-channel veyron_mickey

Steps to reproduce the problem:
1. Enrole Chrome device in GSuite Device Management
2. In the Device Management dashboard under Chrome under Device Settings set the "User data" to "Erase all local user data"
3. Start Chrome device that is configured to run a kiosk app

What is the expected behavior?
The kiosk app starts and the chrome.instanceID.getID function returns an ID that is unique to that device but constant over time (restarts of the device).

What went wrong?
The chrome.instanceID.getID returns a different ID every time the device is started. This happens even if the application identity has not been revoked or expired.

Did this work before? N/A 

Chrome version: 70.0.3538.76  Channel: stable
OS Version: 70.0.3538.76
Flash Version: 

From the official documentation (https://developer.chrome.com/apps/instanceID)

getID chrome.instanceID.getID(function callback)

Retrieves an identifier for the app instance. The instance ID will be returned by the callback. The same ID will be returned as long as the application identity has not been revoked or expired.

I conclude from this that the getID function should return the same ID over restarts of the device even if the user data is deleted, since I see no relationship between the deletion of the user data and the application identity being revoked or expired.