True. And HR is not necessarily this intelligent diabolical force "protecting the company". They are often the biggest source of company gossip! If they see you on their level, they'll say all kinds of stuff. They probably assumed this manager would have some sense and stop getting drunk and touching abs, and then went into ass-covering mode when she went on the warpath.
When you have a division between salary and wage workers, HR has a certain role. Between managers, its all politics.
A systematic and impartial third party review of Google's HR incident and report system's records and/or HR incident related communications records would likely indicate just how much they did, or did not, think it would be an issue.