Google has changed some permissions for usage of Android 6.0 Marshmallow by OEM’s on their new devices. It seems fr the first time Google is making some features strictly available for devices having Marshmallow onboard.
Google’s Android 6.0 Compatibility Definition Document (CDD) explicitly requires Marshmallow phones to include Doze, Full-Disk Encryption and few other features. Here’s what Google says about each feature:
8.3. Power-Saving Modes
All apps exempted from App Standby and/or Doze mode MUST be made visible to the end user. Further, the triggering, maintenance, wakeup algorithms and the use of Global system settings of these power-saving modes MUST not deviate from the Android Open Source Project.
9.9 Full-Disk Encryption
For device implementations supporting full-disk encryption and with Advanced Encryption Standard (AES) crypto performance above 50MiB/sec, the full-disk encryption MUST be enabled by default at the time the user has completed the out-of-box setup experience. If a device implementation is already launched on an earlier Android version with full-disk encryption disabled by default, such a device cannot meet the requirement through a system software update and thus MAY be exempted.
If OEMs attempt to remove, alter or even improve this feature, they would lose Google certification for their product, so manufacturers are going to have to play ball here.
You can check all the features of the Android 6.0 Marshmallow.