Moto X app screen suddenly scrolls vertically
Moto X (2014) by default uses Google Now Launcher as the default launcher.

The Google quicksearchbox was recently updated to give a peek into upcoming Android 6.0 Marshmallow app drawer layout which has vertical scrolling for apps and widgets. 

So Uninstalling the updates for app named Google with package-name com.google.android.googlequicksearchbox  (either in Play-store or in App settings) should bring back the old feature.

User reviews dated 24th, 25th September on Google play-store gave me insight on this that the app named Google caused this behavior.