Are you sure about this? I have seen posts on ZTE board saying that apps can no longer be enabled/disabled with B27. With B20 you can at least do disabling (I am not sure about enabling).
That was something else that was changed.
On B20, if you disabled apps in Settings > Apps, sometimes you would not be able to re-enable them.
(What you're talking about) On B20, if you use the Stock Android theme, if you press and hold on an application icon, there's a "Disable" option at the top of the screen that you can drag the icon to. Using this method, you could disable apps that you couldn't via Settings > Apps, such as the ZTE Calendar and Messaging apps. However, this allowed you to disable things that could cause issues with the device, such as disabling Settings or the Dialer. If you disabled apps this way, you could not re-enable them via Settings > Apps.
On B27, you can still disable apps in Settings > Apps, and people haven't reported having issues re-enabling them.
On B27, the "Disable" option in the Stock Android theme has been removed. So while you're not able to disable some stock apps, you cannot accidentally disable something that could break the OS.