Well, you still don't need an unchecked checkbox, you can just check if the value isset(). However that said it can certainly make it simpler to have one, especially where you are dealing with checkbox arrays:
You can assume, when the form is submitted, a missing checkbox key from the POST array is an unchecked box. If you rely on jS to provide a value you're more likely to have a screwed up CSV then using PHP.
Good that you're trying to solve problems by thinking laterally though
Anti Linux rants are usually the result of a lack of Linux experience, while anti Windows rants are usually a result of a lot of Windows experience.