There are so many groups and organizations that certify devices for compatibility and safety, so it's not terribly surprising when one of those groups publishes data on something that's yet to be announced — like Android 4.4.3. Earlier this week saw Sprint announcing an update to Android 4.4.3 for the Nexus 5, and today it's the Bluetooth Special Interest Group's turn. In this case it's another "Google" device, the Sony Z Ultra Google Play edition.
The device is said to be running software version KTU72.S1.3013, where KTU72 is a reference to Android 4.4.3. The update to Android 4.4.2 KitKat is likely only a maintenance release with a package of bug fixes, performance improvements, and the like.