Sony recently released Android 4.4.4 firmware for Xperia Z1, Z1 Compact and Z Ultra owners. It seems that within the update, Sony has pulled the Contacts app outside of firmware updates and will now push specific updates to the app like Sony already does with its media apps.
Therefore, those on Android 4.4.4 KitKat are currently seeing a new 6.2MB OTA update for Contacts moving the build number to 16.1.B.3.2. We have not seen this update hit any Sony Xperia handsets on Android 4.4.2 and below. Changes include an enhanced user experience as well as software performance improvements. The APK can be downloaded from here.
Thanks Ashish, Jag, Jonatas and Tuks!