identical top to bottom halves. Manufacturers don't have to deal with extra parts and worry about a set with no hole going out. When installed, the bearing halves contact each other at the joint and are then essentially fixed at the diameter they were made to. In a properly sized rod, there is zero clearance behind them. All the clearance is designed to be on the inside next to the journal.
This is not a Nissan specific design every engine I have ever worked on was this way.