Last year Google announced that Android 5.0 Lollipop devices will ship encrypted. When the first Lollipop devices started shipping, which happened to be from Google’s own Nexus crop of smartphones and tablets, all of them were indeed encrypted straight out of the box. However devices from Google’s OEMs are not shipping encrypted which goes to show that Google is not forcing its manufacturing partners to do so, even though it had initially said that this would be a major requirement.
Clearly a change was made between the time Google first said encryption will be a requirement and when it published the updated hardware requirements for Lollipop devices in January.
The Android Compatibility Definition document now clearly says that encryption isn’t required on new Lollipop devices however OEMs have to ensure that it must be supported. The document does mention that this requirement can be given a permanent status in future versions of Android.
There’s little reason to believe that full-disk encryption on Android device will have any major impact on its performance, that much was evident from Nexus 6 and Nexus 9, both of which shipped with encryption enabled by default.
Google might have eased up on the restriction this time around but it leaves the door open for stricter implementation in the future, and I wouldn’t be surprised when it finally decides to go down that route.