The way it (seems to) currently work is that when you open the friends list, it requests to update, then takes like 5-10s and then actually shows the current status.
For example if you open the friends list when someone is level 10 and then open it again 2h later, it will still show them as level 10 until it actually updates (despite that person having progressed much further already).
As far as I can tell there’s no indicator for this.
It would be nice if it told you from when this snapshot of the friend list is. Also it should probably show some kind of updating icon when you open the friend list to let you know that it will show you the current status of friends if you wait a little bit.