The wording was just an attempt to illustrate the point. There are cases where you can rephrase a sentence with "zero" to get basically the same meaning, but the important thing is that "zero" falls into the same semantic class as other numerals, which other ways of negatively qualifying existence don't.

Put another way, the invention was not literally the word "zero", or anything to do with language per se. It was the idea that you can think about lack of existence in the same was that you think about counting, i.e. treating the idea of there being two apples and the idea of there being zero apples as two examples of the same thing in your mind, instead of treating one as being in some way fundamentally different.

Being raised with a maths education from a young age now, it's easy to see this as obvious, but there was a time in human history when it wasn't.

Also, I wasn't disagreeing with the Cartesian coordinate system being more significant.