Not Option, but Command. If you hold down Option and click in another window, the current window hides. You can also hold down Command and drag a window that doesn't have focus.

You can also switch focus to a window without raising it by holding down Control+Option and clicking the window.

At any rate, a lot of these things can be chalked up to different philosophies, I think. Personally, I really don't like focus follows mouse; when I was using FreeBSD and Linux many years ago, I would try it and then end up disabling it after a short while.

It is worth noting that Terminal has a hidden preference for focus-follows-mouse:

    defaults write com.apple.Terminal FocusFollowsMouse -bool true

You can also change that setting, along with those of some other quirky system things, in third-party apps like TinkerTool and Onyx.