New FireOS 4.6.4 Only for AT&T Fire Phones. Newer than 4.6.3 for Unlocked Fire Phone

I thought that you would like to know that apparently there is a newer FireOS v4.6.4, but only for the AT&T Fire Phone!

http://www.amazon.com/gp/help/custom...deId=201607550

Curiously this AT&T Firmware is newer than the v4.6.3, that we all have received on our Unlocked GSM Fire Phones.

Fire OS 4.6.4 computer:Fire phone (AT&T):

http://fire-phone-updates.s3.amazona..._464000220.bin

Does anyone here knows what's new in this latest FireOS 4.6.4 Firmware update?