Is it normal for WIP (Job) reservations to go away after partial shipments when there is still QTYl

We are having a problem with  DJ / SO linkages going away after partial shipments. 

Simple example:    We have a sales order line for lets say QTY = 10.    We create a WIP DJ for that item of QTY = 10.    Lets say we complete 6 of the 10  parts on the DJ.     At that point we have 6 inventory reservations to that SO line and 4 Job reservations to that line.     If we ship confirm the partial line quantity of 6  after the ship confirmation the  DJ / SO  link for the remaining quantity of 4  is gone. 

Is that normal functionality ?        We are on version 12.1.2  and I could swear we tested this in prior releases I we did not lose the link.    The link would follow the line split  ( say from our example from  1.1  to  1.2 )