Huh, I see my answer to my own question was removed for some reason.
For anyone else that is searching for this sort of thing, the fix was to tweak:
ToastEnabled
NoToastApplicationNotification
NoCloudApplicationNotification
NoTileApplicationNotification
In SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\PushNotifications & SOFTWARE\Microsoft\Windows\CurrentVersion\PushNotifications
DisableNotificationCenter in SOFTWARE\Policies\Microsoft\Windows\Explorer
and
TaskbarNoNotification in SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
of the HKU hive for the KioskUser & the first 4 keys in the HKLM hive too.
I'm going to leave extra detail out in case that was why the previous answer was removed.