The Apple article does tacitly mention:

You might want to change your password for other accounts, too.

Personally I would trust iOS security enough to not be too worried. Especially if I can issue a remote wipe in a timely manner. As long as the phone isn't swiped out of my hand while unlocked, I'm doubtful the average thief will be able to get past the lock screen. (Though I'm also assuming the thief doesn't have my passcode)