Say you have two j-boxes, A and B. The hot and neutral of a lighting circuit comes into A, goes to B and proceeds further where it feeds a switch. The switch leg makes a circular path around the ceiling, comes back to B by another route than the hot, goes thru B to A and leaves A by a route other than the original hot feed came in.
Would you require there to be a designated "hot" neutral and a designated "switch leg" neutral in the conduit between A and B?
If you used the original neutral that came thru with the hot between A and B to also serve as the neutral for the switch leg, since they are actually the same neutral, would you in reality create some kind of neutral loop that would balance and divide the current between the load on that switch leg and any other load that happened to be downstream of the switch?
A break time breakfast is riding on this.