Maybe, I don't have any other MDI applications at hand. But the point is that if any existing window is unminimised then it will return to its maximised state, so it seems counter-intuitive to me that a new window would somehow "break" the maximised state. Consider the following situation:
* Maximise windows
* Minimise all windows
* New window opens in restored state
* If this window is left open, unminimising the other windows will cause them to also be in a restored state (obviously), whereas if the new window is closed beforehand then the original windows will retain their maximised state when they are unminimised.
It seems like it would make more sense for any new windows to be maximised in this situation, regardless of MDI's traditional behaviour.