Why does it scare you that they put out an update to change how they work with what is essentially irreversible hashes of the original high resolution scan of your fingerprints?
Because those hashes, when leaked to an outside party with a big database of fingerprints (say, the NSA), can be easily be combined to find matches in that database and identify somebody. Hashes don't solve all the problems, cmelbye, the identifying info is still there!
If the NSA gets access to your phone, there are hundreds of easier ways to identify who you are than having to go through the schlep of reconstructing your fingerprint.
You did not understand me correctly. The problem is that this can be done remotely, over the air, even when you're not in the US.