Is it possible for the maxilla to be pushed back?

You are correct that the lower jaw can be pushed back or advanced forward, while the upper jaw(maxilla) could theoretically also be pushed back or advanced. I cannot think of a case I have ever had to do this, more commonly the maxilla needs to be advanced, and depending on your facial aesthetics, the size of your lower jaw and the jaw relationship discrepancy, the lower jaw could be pushed back at the same time. Hope that answers your question.