Yeah its a useless update that does absolutely nothing
All the major carriers (in the United States) are fixing to roll out the new emergency alerts tomorrow (Sunday). I read an article somewhere in which Sprint stated they could make their phones capable of receiving the alerts with an OTA update. Therefore, I believe this is what the update that just came out is for.
More information about the alerts: Wireless Emergency Alert System Goes Live - Government - Mobile & Wireless - Informationweek