I suspect it might have more to do with a significant misunderstanding (and very common... basically everyone falls for it the first time) of how MFDs work rather than with multiple pages.This is probably another issue with my understanding how to render multiple page MFDs.
There is a reason why the orbiter API talks about MFD modes, rather than just MFDs. An MFD mode is a singleton. Only one instance of each mode exists in the simulation. You can even open the MFD in another vessel, it will still be talking tothe same instance in the back.
If you want the same MFD mode to work concurrently with different data in different MFDs, it needs to manage data and state of the various instances by itself. At least that's what I remember of it...