Does this slight variation in the outliner represent a different hierarchical connection?
See Pic.
Yes – Spine1_CONTRL1 and Spine2_CNTRL_GRP are both siblings and both children of Spine1_CNTRL1_GRP whereas all of the items above that in the hierarchy have only one child each
The likely difference is that as shown here, if you move Spine1_CNTRL1, Spine2_CNTRL_GRP would not move.