hard or soft copper line for a valley oil gallery bypass line?

No, I'm saying even IF there is a pressure differential at some point you will have pressure and no flow. But you assumption that the pressure is equal throughout the engine is incorrect.
That is not my assumption. I didn't say pressure was equal through out the engine. I'm trying to figure out how having opposing feeds in the gallery stops flow at some point in the system. Can this only happen if the pressure is different at each end of the feed? or will this still occur if the feed pressure is the same on each end?