Hmm. That path doesn't seem to work on my Nexus 4 running Android 4.2.2. The closest I could find is Settings > Backup & reset > Backup my data (Backup app data, Wi-Fi passwords, and other settings to Google services). Tapping this, it says "Stop backing up your Wi-Fi passwords, bookmarks, other settings, and app data, plus erase all copies on Google servers?". So, it sounds like it's all or nothing.
Phew! It appears that my instincts were correct when I first turned on this device.
I keep wifi passphrases in a location that is just as secure as the ethernet network to which the wifi is tied: on a piece of tape on the bottom of the WAP. Looking at this again, in the unlikely event I forget the passphrase, seems not to be a burden.
Thanks, that path you posted applies to my phone too. It looks like the Backup setting was already off for me. It might be one of those settings that you are prompted about while setting up the phone.
