Because the galaxy is the same for every mode. Mission stacking a la Sothis wouldn't have worked as it did. This is the evidence mission board can't be the same
to all at a specific point in thime, sadly which leads to conclusion it must be created on the client by radomizing a given range.
Regards,
Miklos
If you refresh the board long enough you will see exactly the same boards come up, same missions in the same order. What is random is the boards that are presented to you in that instance, two players in the same instance same board. But there is a limited set of boards to be presented with, until the server freshes creating another set.