It seems to me that this person is trying to find a dead circuit. All to often when you open a box you will need to find the main hot wire.
Since there are 4 black wires and 4 white wires, more than likely one of the black wires are hot and the others are circuits leading to lights or receptacles.
Having someone below the ceiling to check the lights and receptacle plugs while you're in the attic is necessary to complete the job sufficiently.
All to often there will be one hot (black wire ) connected to a light circuit and the others go to the receptacle plugs.
Usually, when I run a three or four-legged circuit I will cut off a least 3/4 of the insulation to ensure that the wires will connect properly inside the wire nut.
Looking at the picture I noticed the ends of these wires are really short, so I can only guess that maybe there are two hot wires located inside the box that are tied too different circuits.
If I was going to leave the box open and couldn't complete the circuit, I would make sure that all of the wires are covered with a wire nut.
Using a line voltage detector also will work outside of the box checking for wires covered with insulation.
When I check for dead circuits I usually switch off the breaker and have someone below the ceiling to check: first for voltage, not all receptacles within a room are connected with the same breaker. You may also find that a receptacle has been split into two different circuits. Such as the top of the receptacle continues to go around the room to complete the circuit and the bottom part of the receptacle operates a lamp with a switch located on the wall.
If there is no voltage then check for continuity within the circuit, where the box is located above the ceiling I will connect the black and white wires together to make a continuous loop to see where the wires may be connected below.
This person below the ceiling will check each receptacle and light to see if they are getting a continuity reading.
Hope this helps.