What's in an ‘a’?

When do you know that you’re correct? For me, in the world of grammar, the answer is rarely.

I’m reviewing the changes made to a paper of mine by the production team at Elsevier, and they’ve changed my sentence

An example of a system with such behaviour is…

to (emphasis added)

An example of a system with such a behaviour is…

Well, doesn’t look right to me. And Google reports half as many hits for the latter compared to the former.

But I’m not confident enough in my knowledge of English to call them out on what looks to me like, at best, a matter of style.