It is considered very bad form to send in a drive for service under warranty when you ruin it during flashing an unofficial firmware. That being said, it would be very unlikely that the firmware indicated above would be the cause of a failure.
And yes, if the drive is defective in some way and you are not responsible for the damage, then you can reflash back to the factory firmware and send it in.
Keep in mind, if the drive totally dies, you won't be able to flash any firmware, but then neither will the repair center. In any case, most of us here consider the risk to be small and the reward to be high, so we flash. MAKE SURE THERE IS NO DISC IN THE DRIVE AND BE PATIENT AND DON'T INTERRUPT THE PROCESS. Also make sure you flash the correct drive. Those who are paranoid often disconnect anything but the drive they want to flash. We all make mistakes.