The "Group By Date" inbox setting is now enabled by default in Notes v12. When enabled, messages in the Inbox > All Documents view are grouped by relative date. To disable, users need to manually select Show and uncheck Group By Date in their Notes Client.
For other users, this specific setting is causing inconvenience as it require them extra clicks to see their mail. It also requires extra clicks to manually turn off the setting. Allowing a notes.ini parameter or managed settings to turn off this setting via mail policy or desktop policy is a more feasible resolution when deploying the changes for all the users who don't want this feature enabled.