Let me try and help you understand Greavsy.
I want to move my season ticket to another seat, so I toddle over to the ticket office and say "hey there ticket person, I want to move my season ticket".
They then look at whats available, and reply "Look, theres this seat here if you fancy it?"
If I do I then transfer my season ticket to said new seat, and then, heres the bit you''re clearly missing, my old seat becomes available, therefore no queue has been jumped, and no seat has been taken from anyone on the waiting list.
Hopefully this helps you understand.