I personally don’t agree with that view point . You def are in the minority in today’s world . Having commuted for the last 10 or so.
The whole non rev thing goes in seniority regardless of which work group you are in , pilot , FA , ground ops etc .
So by having a senior 87 hire ride the back and allowing the 2015 hire to sit in the Jumpseat , no seat was taken away from that ground ops fellow , him nor any other group besides the pilot group had access to that jump seat at any point.
The seats in the back of the airplane are the ONLY ones that other groups access too , so I don’t see it as you describe .
Respectfully don’t agree with your view point .