What is the 'Activity Suppression' method?
Android Enterprise (AE) devices, by default, are in Native Mode when the Kiosk configuration is applied. This is a true whitelist where applications are pinned to the screen, so no other applications can be opened. Furthermore, device buttons and the status bar are disabled in Native Kiosk Mode.
Administrators are now able to setup a Kiosk Configuration with device buttons, and the status bar enabled via 'Activity Suppression' Kiosk Method for AE. This method works by checking if the foreground app is whitelisted; if it is, it allows the app to remain and if it is not, it will push the app to the background. Activity Suppression Method can be configured from the 'Advanced' Option found in the 'Kiosk Mode' Payload in AE profile type.
On Android Plus (A+), when Lockdown is configured, by default it will be utilizing Activity Suppression Method as well, where non-whitelisted apps are pushed to the background when opened.