It appears that udev calls BLKRRPRT on a block device whenever it gets an inotify event that some other process has closed an fd to it. This causes all of the partitions on the disk to be deleted and ( hopefully ) re-added. This makes for a lot of seemingly useless udev events.
Even if they are re-added, this causes a race with other processes on the system and can cause them to error because the partition disappeared. Worse yet, the kernel may not even be able to read the partition table on the disk ( it may have been provided by command line or use of the partx tool ), in which case, this would just delete the partitions. Why does udev do this and could it stop?