It was July Arrrgghhhhhhh :-(
There are a few issues with the Android 9.0 updates which is causing a few issues with Kiosk device builds and the Fully-Managed builds.
I have a few tickets open with MS on Kiosk build issues. I spent the majority of yesterday talking to specialist engineers from Europe and North Carolina trying to sort some of the issues out. One of the issues is that Android 9.0 has either moved, removed or replaced the way quite a number of Dialogue UI's work. Where some were retired in 8.1.0 etc. Intune was able to still auto configure a setting as enabled or granted. Now with 9.0, some of these are behaving as if the legacy settings have finally been removed. This does not affect all MDM's. For example in the old world of Android Admin you could Disable/Enable the Power Dialogue UI so that devices could be set so that the power button would not allow the "Power-Off / Restart" dialogue to appear.
Intune, in Android Enterprise, no longer has this setting/key-pair listed as an option. The result is; Intune Kiosk and some of the newer Zebra MX devices cannot be switched off or restarted whilst in Kiosk mode. They can still be restarted via the console. Hopefully these issues are sorted and it will go GA asap!! Fingers Crossed!!!!!