If split on the outbound, it does appear the non-status individual loses all inherited priority benefits. At check-in, if with UA, you can "recover" the bag allowance waiver. If E+ seat assignment is lost (such as in a plane swap), a call should be able to restore.
Since they can board/security (but not PreCheck) with you, no problems there.

But the upgrade priority is lost, GA may be able to restore.