So Apple released a faulty update, pulled it and told affected users how to roll it back. It happens.
Believe it or not sometimes a defect in a release can slip through any QC process - the notion of 100% perfect quality control is an illusion. For example, Android users (I know from experience at the time and it is documented online) had OTA updates for Froyo, Gingerbread and even Jelly Bean that literally bricked phones and tablets. It doesn't excuse Apple and I hope they are also investigating how this bug got through testing but it does show that these things happen no matter how well you plan and no matter your intentions.