So instead of waiting 10 or 15 minutes (I forget how long it is for it to auto-refresh) you can just switch game mode and it auto-refreshes the bulletin board with different missions?
If so, NICE!
It's not strictly true.
What happens is that on load, you're allocated a server. Try it. On the main log in screen (main menu) look at the bottom. First time you log in it'll say server unknown.. or something similar. Log into the game, and log out back to the main menu. It'll tell you what server you're about to log in to. I.e. server 448. If you log in to server 448, you'll have missions. If you go to open and suck out your 'power generator' missions, and log out, you'll either be connected back to server 448 or another one. If you're now connected to server 549, and go back to open mode, you'll have new missions. If you're back on 448, open will have no new missions. The most I noted was 4 servers online at any time. maybe 5 at a push. It's random what one you connect to. If you bounce between solo and open, and log out, you're just jumping between one server and another making it appear that solo and open bouncing are giving you new missions. what happens is that before the servers refresh every 5 mins, you'll dry up the missions. After 5 mins the missions will trickle back. The best bet is to leave it and come back.
I have been grinding Empire for the last week, and you start to notice these things!
TLDR : mode switching doesn't refresh the boards. Changing servers upon log to menu does.