I noticed that the way supply lines are drawn can give away information.
supply lines.jpg [ 83.16 KiB | Viewed 142 times ]
Notice all lines stop short of "A", but happily go all the way to "B" and all the other systems. Since this is turn 1, it is indirectly informing me that there's a space monster or hostile fleet at "A". That takes a little excitement from exploration.
I suggest any unexplored/unknown systems should be treated the same way as hostile systems: supply lines of both types should not
go through them. Our virtual, abstracted transports shouldn't go into utterly unknown systems.
Of course it is possible later in the game that the player would get information of where ships might be from supply lines being cut off, but that at least can have a reasonable in-game explanation: If our abstracted transports are suddenly getting blocked/destroyed, their absence would be noticed.