When I changed the I-485 file to reflect completion of that loop route, I didn't synch or de-synch it with I-85's point 48, I only synched both ends of I-485 with each other. So the NMP wasn't deliberate.
I-485's 30 and I-85(48) points (which have identical coordinates), and I-85's 48 point, are all off-center, and should be re-centered at the same coordinates.