It doesn't matter if you do `off(ev), but if you do `off(ev, fn)` and it doesn't find the matching fn then it isn't actually removing the event listener now is it? We didn't want to rip open the existing jqLite.on() method to pass in another param like jQuery does.

It doesn't break anything, but if you're a developer adding one() and then off() right after on the same event + callback pair and it's not getting removed then it isn't working as you expect it to.