To most people zero equals to "nothing" - something you usually don't try to divide. No wonder, that most people struggle when they are asked, if it is odd or even.
It is clear to mathematicians, but maybe not so clear to citizens. Better to make it clear. Does new York have personalized plates, and how would they be handled?
Vanity plates that don't have numbers are considered odd-numbered plates.
Most people assume that an even integer is an integer whose least significant digit in base 10 is from the set {0,2,4,6,8}
When in doubt, be as explicitly clear as possible. There was no harm in his pointing out something obvious.