Courtesy of Kate , I learnt this new word.

I would attribute the lack of knowledge to never having the opportunity to go into research or even read enough research papers to learn about this word. The only word which came close was probably treaty – which I learnt during history class.

Giving an intelligent guess, the reason for the formation would be to commend on an excellent piece of writing – providing a treat to its readers/audience. Another meaning I found – a formal work on a subject, esp one that deals systematically with its principles and conclusions.
However, due to the word “brief” inserted just before “treatise”, I can safely surmise that the first meaning is probably be more apt in this example.