When I go to Multiplayer -> Join Session and get "No sessions found" message, I never see any session became available although there is written "Refreshing..." at the top of the screen.
But, sometimes, I just type ESC and get back so a session magically is shown.

So I am questioning, do the screen really refresh alone?

I don't think so. I believe it will only update the server list when you exit the screen that says "No sessions were found" and re-select "Join Existing Game." Although I too find it odd that "Refreshing..." appears at the top of the screen.

I agree. But the time spent searching an open server to join seems to be so little.
I think that an adjust in this could help I find more games to play, at least with my current "cheap" net plan.