"Nothing is real", quoting the Beatles song.

When Messiaen built his musical universe from indian decitalas, non retrogredable rythms and bird song, the most important aspect was not whether there is some truth or inner meaning in this. The important aspect is that he creates a belief, -at least for him self, in a language or a system that makes it possible to create something at all. After all it´s just a game. 

I don´t believe that it´s of any use to make a big deal out of systems like this. Every artist has his own system or ideas as guiding lines, but the beautiful thing about it is that it comes out of nothing, that it is man made and surreal. It is impossible to proofs it´s real value.