The answer to your question that was given to me by a WMA manager is, it is up to the WMA manager. The reason they usually allow it is they want to make it easier for people who are older (like your dad) who can't lug a stand in as easy.

The second part of the answer (also from same manager) is, stand up or not, first to the spot gets it. If you are there and set up and someone comes in and says I have a stand 50 yds over, too bad for them, they will be hunting off the ground somewhere else that hunt.

Now if I was on the road and had not walked in, I may or may not give the spot up depending on whether I knew I was there first, etc. In other words, I'd try to work it out with them. If I couldn't I would complain to the WMA manager, because if they get enough complaints, they may stop allowing people to leave a stand over night.