Why are INSERTs and UPDATEs slower on Android 4.0?

When Android 4.0 became available for Nexus S back in December 2011, we did some performance testing: http://greendao-orm.com/2011/12/17/sql-performance-in-android-4-0/

Surprisingly, UPDATE and INSERT performance dropped by half (!) after the Update to Android 4.0 on the same phone. We did not have time to investigate further, but maybe meanwhile somebody else did?

One could speculate, that the file system changed, etc. but I'm looking for hard facts. ;)